Auto petter

[Dreadloki]

Since it's so rare you could add a way to make one through Maru or something and have the player complete some quests to unlock it then buy it from Marnie after having Robin and Demetrius make it

 

[Quirinea]

Hmmm. Most logical could be that Fizz would sell it. (I'm shamelessly cheating with Skull cavern elevator and Timespeed so I usually soon get more than I need)

 

[Freizeitfarmer]

Since it's so rare you could add a way to make one through Maru or something and have the player complete some quests to unlock it then buy it from Marnie after having Robin and Demetrius make it

It is not rare as soon as you can go to the desert Skull Cavern:
Use luck buffs and stair cases and go at a lucky day. Then you can get Auto Petters on Treasure Rooms levels!