- Trash can lid might work if it doesn't have handles on top and you don't have a huge ass.
- Pool inflatables will work but will most likely rip. As a bonus though, if you can find a place that actually has them they are probably really cheap right now.
- If you're crafty you might be able to mount a lightweight piece of wood to two lengths of PVC pipe... or just use the wood.
- I've seen people use snow shovels, but it might end up busting your balls.
It's really a matter of what materials you have on hand and such. If you don't mind buying something just as long as it isn't expensive, get some thick plastic, a small sheet of wood and 2x4 the same width as the wood. Wrap the plastic tight around one side and staple it on the back. Make a lip on the non-plastic side with the 2x4. You sit on the wood side (plastic side down) and put your feet up against the wood lip. Without the lip it's likely that the only sliding will be you, off the edge of the device.