I have QL17-GIII, 7SII, 35RC, and Retina Ia, II, and IIa, and many other cameras.
Under $50, realistically:
1. Oly 35RC.
2. Retina IIa or II. If you are lucky, you may snatch a Heligon. I got my Retina IIa with Heligon with ~$17 ...
But if one can spend ~$100, 7SII with a working meter is unbeatable.