Silver variants of gear should cost more, and “precious” rings should have some kind of surcharge too, above the base cost of that type of ring.

Silver weapons should be rarer than they currently are outside Gehennom and fairly common inside it.

Add a silvery potion, either as a random appearance or a dedicated potion like dNetHack’s potion of silver starlight, which will silver ammunition dipped into it, perhaps temporarily. It might also silver other weapons (spears, daggers) or other items. Random appearances have the possible problems of the potion potentially having a defined dip effect already (polymorph, for example), and it potentially not appearing in the game if there are extra random appearances. Dipping fragile silver items, like silver arrows, into a potion of acid could create a silvery potion.