The issue here is how big are the engines you're trying to convert-the Enya 09 carb is a great carb-but only suitable for engines in the 1-1.5cc range.The original OS Max-10 carb also works well in this mode.... 'Small' to some of us means <0.5cc-to others it may be less than 2.5cc! If you're talking about very small carbs for 0.6cc or less then there is only one option-the PAW55 carb-not in my my opinion a very good one-but that's all that's currently available. The Schlosser 0.5 and 0.25cc were excellent-but no longer available, the cox 05 carb has a 1/4-32 threaded shank-the MP Jet and small Enya carbs are flange fitted. Without decent machining facilities there are not too many options available. The Enya 09 and OS Max 10 carbs have been fitted to the MK-17 diesels in the past and performed well. There might be something available from CS for their small sideports-but availability I suspect is questionable. The PAW 049 and 06 diesels seem to work quite well in R/C mode-I've seen photos of throttled Mills 75s on the Net-but never of a Merlin, or a Frog.... the MP Jet carbs are probably the best designed for purpose-but would need considerable modification to adapt to a shank fitting (for 'modification' read 'machining work'.....)
You could also look at the little PAL 020 engine-I don't know if they're selling the carb separately. The issue with small diesels and throttles in particular is the very small throttle bore required for effective throttling-which generally means a 'specific to engine' solution, and such carbs do not necessarily transplant well to a different brand and size.