I'm painfully cheap at times, and I have two stomp pad methods that I use:
1. Double-face Scotch tape sticks well enough to hold a sheet of material to a board. I have an old 1/4 inch thick foam typewriter pad that I've cut into stomp pads and held with the tape. They've stayed stuck for several sessions of riding, but also come off easily if you want them out of the way.
2. Walmart ('the evil empire") sells 2mm thick self-stick foam sheets in the arts and crafts department. Comes in various colors including black. This stuff sticks very well and makes a stomp pad just as good as the ones you can buy. I forget the price, but it's cheap, maybe a dollar or so for a 9x12 inch sheet.
....Wolf