Jim built 3 different thicknesses. Fat- Fat, Fat-Regular, Little-Regular. Can shoot me a message and I'll email pics. Don't know if pics are wanted in the post.
Dink shoot me a PM. There are a few builders making copies or similar plugs and I know a couple guys that might sell an original, but they are not cheap now a days.
Check and see if you have any local plastics companies. They usually keep a scrap bin to sell by weight or use for their other in house projects. I have gotten a 4'x4' sheet for free before.
PS. they usually have several thicknesses as well.
Contact a local plastics company. They usually keep a scrap bin and sell by weight or use themselves when needed. I have paid next to nothing for large sheets and even been given some for free.