Pianica is just what Yamaha calls it. Suzuki calls it a melodion. Like a previous commenter said, melodica, the generic term, is owned by Hohner since the 50s.
Bought one yesterday at a thrift shop for $10, seems to retail online for $45-65 for the one I got but yeah I always say thrift shops. Just dont forget to disinfect anything you gotta put your mouth on!
I despise cajons. I cringe at the sight of them! Use a snare and some brushes or something. Anything but that stupid wooden, bedside locker looking, piece of hipster crap. Good musicians by the way.