I dont' know if he ships to Germany but Vlad Konokov makes one that works with both Lindsay and GRS fixtures. They are reasonably priced ,variable speed and can be bidirectional. Look him up on instagram.
Skip the argentium and just rodium plate them after engraving if you want to keep them bright. Rodium plating just takes a few seconds to apply. It will stay bright for a very long time if it is not worn and just used for display.
An easy answer is gonna be a little complicated but I think you can getter dun. I make dies for blanking silver rounds and other parts for myself. The texture you want can be obtained with a rolling mill and texture plate. Then blank out our round blank with a simple die and punch using a...