In the US - Beseler 23C's are good. Well built and plentiful. 23C, 23CII, or 23CIII are all good. They all take the same carriers which are relatively easy to find. This is good because when you get a used one, it might not have the carrier you want. They go up to 6x9.

I have mine on a microwave cart and wheel it into the bathroom when I print. Pick one up on craigslist. I found a brand new unopened 23CII for $75 on craiglist.

Oh, and Beseler is still in business, so you could get parts from them.