Lets go back to Raads specific situation,
He lives in Egypt and has stated that he cannot get nitro fuel where he lives.
That is part of the reason he was asking about gas trainers.
I mentioned the G20 as a possible option on a 60 size trainer, Yes it is a heavy engine but alot of trainers (at least most of the ones I have worked with) have needed some amount of nose weight to get a good balance. By the same token, a large trainer doesn't mind a little extra weight.
The G20 is advertised as an engine for 60 size planes, I don't know of any other gassers that small or any trainers large enough for bigger gas engines.
His only other option, unless he finds a source for glow fuel, is electric.