The Schwinn Riverside with 79cc predator

I'm not sure where to buy those exact clamps, but a pipe clamp might and I stress, MIGHT work. If you know your downtube diameter or can measure it with calipers, then go to home depot or lowes and get a pipe clamp that size or as close as possible. It may work and it may not, but they only cost a couple bucks and might get you back on the road. They are likely not to be as strong as the clamp you lost, so I'm going to suggest two things. One, you definitely want to cut a shim long enough to hose clamp to the downtube. Two, if you don't already have the motor braced to the frame (aka third motor mount), I strongly suggest looking into that.