On another note, a hybrid between coin-op carts and Bushwaffles was mentioned...
In Germany, all the shopping carts require a 1 euro deposit before you can use them. Unlike in America where you often see the homeless pushing carts around town, this was never the case in Germany. Everyone wanted their euro back!
Anyways, I did once find a missing shopping cart...no idea where it came from...but it turned into a make-shift scooter:
A lot of grocery stores now have carts that apparently can't roll out of parking lots. Like a shock collar on a dog, once over the boundary of the parking lot the cart's wheels are locked.
I'm not sure what sort of cart/Bushwaffle mix you're looking for, but the idea of coin-op mini bumper scooters that stayed with a small area, like a plaza, came to mind. Most likely too dangerous, but a cart surrounded by inflatable padding sounds really fun!