There's an older version of the Mini from 2005, where Mametchi could evolve into Ginjirotchi (or, in the Japanese version, Lucky Unchi-kun), instead of into Bill. However, those weren't released globally (Japan and North America got them, whilst the UK and Europe didn't, as far as I know), and they're no longer available at retail.
As Berryitchi notes, all that's out there now is the 20th Anniversary Tamagotchi Mini, and Pochitchi hasn't appeared on any version of that. (I think that this is a pity. I'd have happily bought a second Mini if they'd offered a P2-themed version.)