Source Dungeon Denizens Revisited

Aura moderate transmutation; CL 7th
Slot hand; Price 56,000 gp; Weight 2 lbs.

Crafted from a preserved rust monster antenna, this item works similarly to a gauntlet of rust, with the exceptions that you can make a rusting grasp touch attack with the whip at will, you can use it on all non-magical metallic objects (not just ferrous ones), and it does not protect you from other rusting attacks. This item counts as a whip for the purposes of proficiency and weapon feats.

Craft Wondrous Item, rusting grasp; Cost 24,000 gp (28,000 gp if deceased rust monster is not provided)