It's not technically vintage, but you can adapt a Fujian 35mm f/1.7 or f/1.6 C-mount lens.
Can be bought on Dinodirect or Aliexpress for around $20-25.
Buy the black one, silver has internal reflections (even the black one has on the mount, but you can screw it off and paint it black inside to reduce some).
https://www.flickr.com/groups/2062341@N22/pool/Personally, I ordered the newer one in pic related that doesn't really seem to have any reviews yet.
