The Happy Nerding 4x Stereo Mix is pretty good if you don't mind the dual knobs - https://happynerding.com/category/4x-st-mixer/
-- wishbonebreweryHow do the dual knobs work? Do they push in / pull out to switch which channel you're interacting with?
-- Podfrog
They are concentric knobs, with the center one controlling one channel and the outer "ring" controlling another. You can't push them in but they don't protrude that far from the panel tbh. I find them ingenious and love how they save space without compromising playability.