Which one? The majority, save for the one Tinkerbell gives you toward the end of the wishing well arc, are found in treasure boxes in the the large areas of the drone search, nominally during that portion of the story. There are one or two that you buy from Emee, but most are in the treasure boxes, and if I remember correctly the patreon one is actually the one that Tink gives you... at some point. I think you have to repair it somehow.
It's been awhile since I've played through the game, so I don't fully recollect.