Extrinsic sources of acid resistance should protect your weapon from passive corrosion attacks, and extrinsic sources of fire resistance protect your armor from taking fire damage.

Artifact ring that provides a cocktail of basic resistances all at once (fire, cold, shock, poison, maybe sleep, maybe acid). This is interesting primarily because it is very useful early in the game and then becomes progressively less useful later on as the hero gets intrinsic resistances.

Could be named “The Ring of Everything Resistance” or “The Chromatic Ring”.

Potion of acid resistance, which true to its name confers temporary intrinsic acid resistance.

Give all mimics acid resistance, because they have that in D&D.

More acid resistance sources in FIQHack, to balance yellow dragons’ exploding acid breath. Possibly a ring or amulet of acid resistance.