Alright, you asked!!!
I was following some threads on another forum - don't remember which. They were making recoil pads/buttplates from flip-flops! It sounds too stupid, I know. But in fact, they looked pretty good. I have gone so far as to dig up some plexi-glass (for a backer) and buy some flip-flops. I plan on glueing the shoe sole on to the plexi-glass so it resembles a conventional pad. I'll have to predrill the holes, but that's no biggie. Clearance holes for th flip-flop, and countersunk holes for the plexi-glass, then glue them up rith some urethane glue.
Sounds crazy, but they oughta' work! Best part is, You'll have about $5 invested, tops. Make a visit to your local siore, and pick out a sole pattern and color you can live with. I elected to go with the hexagon sole pattern, in basic black. OD green was a close second.