Hi
2 wheeled handcycling is a obsession of mine!! I bought a varna 2 wheeled handbike as seen on you tube "2 wheeled handcycling" it can be ridden without leg use but takes practice and isn't very practical other than on track. Although I expect in time it would be possible.
I have also built one myself but haven't quite got it right
Twicycle are bringing out a hand powered racer and its pretty cheap.