I am probably not the first person to do this but I am so happy with the results I thought I would share.
Being unemployed I cant afford a nice fizzy mold machine and didnt like the uneven backs I was getting on my fizzies. I also wanted to standardize them a bit. So I went looking for a solution. I bought a 2 inch plumbing connector (bar code # 1194203337) from Home depot for a buck. I think found a pvc bushing ( bar code # 4908113326) that has a lip on it, also about a dollar. The bushing was hollow so I filled it with resin (see picture). The resin was the most expensive at 15+ for the box. The good part is that I was able to make 2 "tampers" out of the bushings and I have resin left over for later.

It may be hard to tell in this photo but they are 2 inches across and right at 2 inches tall and are just enough for my garden tub


having made my own fizzy mold? Priceless