I think there was a model bipe called a Bolero or something like that, can't remember who designed it but it was sold for a number of years that had a trike gear. I always though it looked pretty good.

Several years ago a bipe was flown at the RC world aerobatic champs by Tony Frankelwitz (please excuse the spelling) but I can't remember if it had a trike gear or not.

Most bipes are indeed built as scale models of full scale which use the conventional gear because it works good enough and is lighter than a 3 wheel gear. A nose gear to take any loads needs to be heavier than a tail wheel.

If there were a lot of ground handling maneuvers in pattern flying and a pattern that needed the qualities of a biplane you would see a lot more trike bipes.