Been shooting half frame since 1971, started with a Pen viewfinder type camera, the early, all manual camera. This has been my personal experience. The original standard Pen viewfinder models seem to be to most likely to work. They have a Copal, two blade shutter with speeds of 1/25-1/50-1/100-1/200 and 'B', a projected frame viewfinder, focus by scale to just less than two feet. With the 28mm f3.5 lens, scale focus (estimating the distance and setting that value on the focus ring) works quite well. I have/had several of the Pen S models with the 5 blade Copal shutter and every one needed service for gummy shutter. Never had any EE models, I want all manual control and the basic EE with the 28mm f3.5 lens has a fixed focus lens, too limited.
If you don't mind a larger camera you can get a Pen F with interchangeable lenses. The problem there is finding lenses, they are getting mighty thin on the ground. The Pen F, FT, and FV can all be good but.....you have to be very careful about operating condition, they can be jammed up and hard to source repairs for.
The Pen viewfinder types with fast lenses, the D, D2, and D3 can also be found. The 32mm f1.9, 6 element lens is also scale focus and very good optically. Don't expect the meter to work, just use a hand held meter, anyway, it is uncoupled and not very sensitive.
There seem to be a fair number of Canon half frame cameras available. The only one, specification wise I'd be interested in is the EE 1.7, which despite the EE designation has all manual control.
Another thought. Kevin Allan is right about camera size. I have both a 35RC and several Pen cameras. The however is; the RC is not half frame so, if you want half frame for triptychs or the 3:4 aspect ratio the Olympus Pens are the best choice, in my opinion. The Pen standard (all manual control) is also more compact in thickness than an RC and feels smaller in the hands than the numbers suggest.