I am far from being a major player here.
Nonetheless, and with all due respect, I find the idea that in this day of
global access to information via the Internet there is some meaningful
reason to believe that folks on any two continents can't lend each other
a hand to be just not right.
Let me be up front: I don't know very much about diesel technology.
That said, the idea of a diesel sidecar rig is intriguing to me...
and a diesel hybrid three wheeler even more so.
In less than five minutes on the 'net I found this:
Green Car Congress: New Diesel Mild-Hybrid Powertrain
Green Car Congress: Update on the AVL ECO TARGET Diesel Mild-Hybrid
It looks like the diesel is somewhat oversized/powered for the OP's needs.
Still, I suspect that some members with a real fondness for diesels have
some special knowledge of small diesels or diesel-generators that would fit
the OP's needs. He can then contact the source, where ever they might be,
and with some luck -- and maybe a little bribery
-- import a power
plant that is perfectly suited to his needs.
Oer Al, I wish you the best of luck in your endeavor.