I don't often post here but, yep, they do exist & a company called Nova make some very good ones, either single "trays" or multiple "trays". I have a 4 "bath" fibre paper processor for when I have to relocate to somewhere smaller and the footprint is tiny compared to 4 16"x12" trays.
Agitation I think is the main issue, it is easier to rock a tray than jiggle a print in the "slot" but something one would get used to.
Nova darkrooms in the uk make/stock the processors. Hope that is of assistance.