Flywill is on the mark on all points. A nice exhaust system from Central Hobbies would be a nice addition. Central carries all YS engines. They are a bit more expensive than the Saitos but are worth every cent. Another possibility is the OS120FX 2 stroke which is still in production. Not as strong as the Bully120 but close; it's a side exhaust engine tho. OS also makes 4 strokes

Or you might consider a Webra 145 or OS 140 2 stroke. They take the same exhaust pretty much as what your plane came with. These engines are no longer available from a manufacturer but many guys have them used in their shops and you should be able to buy one for a couple hundred. They most likely will need bearings. Some guys may have NIB engines as well but still expect to pay less than a new price.

A totally different approach would be to get an OS GT22, a gasoline engine. About as powerful as the Bully when piped. Except this set-up would be a few ounces heavier overall than either the 2 stroke or 4 stroke glow

You have options.....