My bass clarinet is a 'walking' or 'marching' bass - it does not have a floor peg or at least a clamp to attach one.
The bassists (tuba) in my band have fancy tuba rests, and while browsing the hardware store for some useful contraption, all of a sudden I had the idea of taking an unused car jack stand (amazing what floats the basement of a 40-odd year old man, eh?)
I heavily padded its business end with felt (formed so that the bell wouldn't slip away), et voilą, the Two Ton Bass Clarinet Rest. It's even adjustable, and no modifications to the clarinet are necessary.
For the upcoming church concert, I'll probably paint it black...