Stantler also gets the Frisk ability, but Shuppet/Banette is a lot easier to come by than Stantler.
All Nincada and Butterfree get Compoundeyes - the ability can appear on Venonat and Yanma as well.
To get the best out of both abilities to find the item you're looking for, put the Compoundeyes Pokemon in your party's first slot and let it get KO'd in a battle, and have your Frisk Pokemon in the second slot. Compoundeyes will only give you the item bonus if the Pokemon with it is first in the party, regardless of whether it is fainted or not. With it fainted and the Frisker in slot 2, you can send out your Frisker immediately whilst keeping the Compoundeyes Pokemon in your first slot (and thus getting the bonus from it.)