... I had a Rollei 6 x 6 model years ago....sold it...but I still have a cheaper totally manual 6 x 6 Bell & Howell that works fine...I gave $25 IIRC...it may not be quite what the big name projectors are but it
makes me drop my jaw when I use it to look ay my 6x6 transparencies...plentiful on the bay...not as common as 35 mm but they are still out there and go cheap