It seems no one else in the Spanish-speaking world uses that term.
This blog gives two similar, but slightly different, origins of the word: both agree on being derived from "safety can", but not as an "ash tray", but:
Zafacón is the word for trash can. ... Supposedly it comes from the English "safety can", which is, as far as I can tell, a name for trash cans in labs. We theorized that, since there are so many pharmaceuticals on the island, and they probably had special "safety cans" for the chemicals, they changed the English name into Spanish.
Zafacon does originate from the English term safety can. ... Zafacon can trace its roots back to the early 20th century. When the US came to the Caribbean and Central America they feared malaria with good reason. Spraying liberal amounts of toxic chemicals and basic hygiene were seen as the best way to combat the disease. As a result, trash cans in the canal zone in Panama, all over Puerto Rico, and I imagine Cuba were labeled safety can. These trash cans had locking or latching lids to keep mosquitoes out. The word was spanglicized and zafacón was born. It stuck in Puerto Rico, and I believe Panama. Cubans may even use it as may Nicaraguans, but that is about it. ... It is a tropical word born from the confluence of malaria, English, and Spanish.
However, another comment gives a totally different origin:
Cuando a Puerto Rico llegaron los españoles, con ellos llegaron un gran número de árabes de forma clandestina justo después de la derrota del dominio árabe en la península ibérica. ... La palabra Zafacón proviene de un pequeño envase de barro que los árabes tenían en la cocina para echar los desperdicios que se les daba a los cerdos. Este envase en árabe se llama Zafaca y el puertorriqueño la convierte en Zafacón.
This second origin of the word is also discussed here:
The most popular story explains that the word comes from the English phrase “safety can” or “save a can,” but linguistic experts are skeptical about this version. They don’t find a logical explanation on how a phrase that starts with S evolves into starting with Z. The other argument that debunks the “safety can/save a can” hypothesis is that this word is also used by our neighbors from the Dominican Republic. How two countries independently developed the same word and usage does not have a credible explanation? The best hypothesis is that zafacón comes from the Arabic word zafa or zafaca which means a clay container or vasija. After the end of the Islamic Era in the Iberian Peninsula, Arabs came along with Spanish to conquer the new territories. After Latin, Arabic was the second-largest language that influenced Spanish.
Zafacón is, indeed, registered in the DLE since at least 1970:
1. m. P. Rico y R. Dom. Recipiente para recoger las basuras.
The reason is that when the US invaded the island after the end of the Spanish-American war, the troops would set up posts as they moved from west to east in the process of taking control after the Spanish ceded the island as spoils of war (allegedly to pay for the costs of the war). Smoking was very common, so each post would have a large trash can full of sand that served as a giant ashtray. The can was stenciled with the words "Safety Can" for obvious reasons. From there to "zafacón" is but a skip and a jump.
This explanation was provided to me by my great-grandmother, whose family emigrated from Spain to the new world, and experienced the events first-hand.
There seems to be a consensus about the origin of the word zafacón coming from safety can. It is noteworthy to cite this text by Augusto Malaret from 1944:
ZAFACÓN. (Del ingl. safety can 'recipiente de lata'): 'recipiente de hoja de lata para recoger la basura'. (El pueblo portorriqueño, que no pronuncia la z, cambió en z la s del vocablo inglés).
It is indeed funny that the expression safety can was adapted as zafacón and not safacón given that in Puerto Rico people don't pronounce the z sound as in the European Spanish. Augusto Malaret was a Puerto Rican linguist who first published his Vocabulario de Puerto Rico in 1917.
In the Fichero general from the Royal Spanish Academy we can find some files with information, the first one by Malaret himself from 1925:
ZAFACÓN. -m.- P. Rico. Recipiente hecho comunmente de hoja de lata que se usa en las casas para echar provisionalmente la basura.
The first text I can find that uses the word is the following one from a bulletin from 1921:
Tan pronto como el maíz esté completamente seco se debe poner en un receptáculo herméticamente cerrado y fumigarlo con sulfuro de carbono. Si es poca cantidad de maíz se puede usar una lata o un "zafacón" [...].
Note the use of quotation marks that indicated that the word was a recent creation or maybe still not widely used.
Still, there are some linguists that doubt the etymology coming from safety can (why that z instead of an s?), as recorded in some other files from the Fichero general (but those people do not seem to provide an alternate origin). Maybe that's why the Spanish Academy does not provide the etymology of the word in its dictionary.
The use of the word zafacón in Puerto Rico precedes the American invasion (1898), therefore, it has no relation to safety can. The expression Safety can was mostly used in the US industrial jargon and that phrase has never been common in popular American English. Others say that zafacón came with the emergence of pharmaceutical manufacturing in PR, but manufacturing of US pharmaceutical products in PR did not start in earnest until the 1960s. Even Puerto Rican nationalist Pedro Albuzu Campos used the world zafacón on his speeches back in the late 1920s! Zafacón is an adaptation of the Arab word zafaca- a small clay pot used to collect trash, etc. Another example of Arab words adapted to Spanish is ojalá from La-shaa-Ala (Meaning God permitting). Why Arab words in Puerto Rican Spanish?...because PR was colonized mostly by Andalucians that brought Arabs and other immigrants with them.