There is a bunch of videos on youtube. You can go expensive with a press, or use some good gloves and a heat gun. I have made a couple PVC knife sheaths and one holster. I still like leather better than PVC or Kydex. Veg tanned leather after wet forming and hot wax treatment is as tough and plastic as kydex, and it will not stress crack. I have made a couple neck sheaths from lace ends, then hot waxed them after wet forming, and both have the click when the knives are put in or out like kydex. I can count on them lasting longer than kydex.
The PVC holster was easy to make, but neither my wife or I care for it. I may sell it on Ebay eventually. One of the things you have to be careful of with kydex is heat to the gun during forming. Poly guns can get damaged with enough heat to form kydex. I would not do it on a Glock unless you know what you are doing. The pros use pot metal castings of the original guns.
If you are making a holster for any tupperware gun, I highly suggest you go with leather. There are videos online for wet forming and hot waxing leather.
Scroll to bottom of page. You can easily make one holster from a lace belly. The weight is only 5 ounces so it is easy to work with, but once it is formed and then hot waxed it is as tough as kydex. If you do not want to stitch you can use grommets just like kydex. After waxing it will be very dark if you use brown, and black will be very deep. With simple tools you could have a nice tough holster for under $10. You can use tea candle wax from the dollar tree, or dollar store. I do not suggest using candle wax unless it is pure beeswax candles. Beeswax is the best, but tea candle do fine as they have a higher melting point than most dip candles.
The best part is you have a easy to make inexpensive holster that looks like leather but is tough or tougher than kydex.