is another source for engines.
But you need to call him on the phone as his website hasn't been updated in quite a while.
In the USA you can order model engine diesel fuel via Tower Hobbies.
There is a diesel engine category in the forums at RCUniverse.com.
Davis Diesel Development can pretty much make a diesel head for most any model engine you want to use. They already have diesel conversion heads ready to ship for many engines too.