Transmute Artifact

Sacrifice an artifact. If you do, search your library for an artifact card. If that card's converted mana cost is less than/equal to the sacrificed artifact's converted mana cost, put it onto the battlefield. If it's greater, you may pay [Variable Colorless], where X is the difference. If you do, put it onto the battlefield. If you don't, put it into its owner's graveyard. Then shuffle your library.