I've had luck with these guys:
Setecom, in Heredia.
(506) 2293-5586
setecom.com
They mostly sell Generac which is a great generator. Gonna be expensive. Yeah stay with the diesel and stay away from propane...propane is a huge pain in the ass. Last time I talked with them ( their main tech Hector) he also told me they were getting some Chino generators for good prices....not sure how good they are.
Good luck