You can find Polaroid backs for some 35mm SLRs for very low prices now, if you look. The image isn't full size, but if you just want to proof your exposure and lighting, it will work. Getting a medium format camera with a Polaroid pack film back might be better than the 35mm ones, and it could be cheaper than a dedicated Polaroid with manual settings. In any case, you'll want the Fuji 3x4 pack films (peel-apart, not integral film). As far as I know you can get 100 ISO color and 3000 ISO b+w.