You can duplicate parts with silicon molds and casting resin.
Molds has two kinds called one side mold and double side mold.
I comments about one side mold in this page.
The one side mold can only duplicate flat things.
(Medal form, Plate form)
*Details of duplicating parts with a double side silicon mold are here.
At first, watch video. (This video is about double side mold)
-How to make silicon mold
1.Make original form
Make original form with Plastic sheets, Polyester putty, sculpey.
5.Mix hardner of proper quantity harder with a stick.
Proper quality is written in a package.
6.Drip silicon from the stick to the original form. And cover the original form.
Don't pour in one go. Air bublles are made if do that way.
After covering, spray air with Air duster. Air bublles are disappeared.
8.Wait untile hardening.
Hardening time varies according to commodity.
Early thing is about 8 hours. Slow thing is about 24 hours.
9.Take off frames
1.Paste Silicone Barrier with paint brush.
Taking off becomes easy if painted this.
You can take off if don't paint this. But the mold becomes to easy to be
-Store:D.I.Y shop,Toy shop
-Price:1000Yen (about 100Yen = 1dollar) The commodity of this photo is sold only in Japan.
But, I think there must be similar things in outside
2.Fit nozzle to can of casting resin.
This is commodity of sold separately.
It's easy to pour if you fit nozzle.