Cascadilla
Well-known
Ironically, because both the Planar and Orthometar were originally intended to be more economical than the Biogons, they tend to me more expensive due to their rarity. I have both, and they are good lenses, especially the Planar since it is coated and the Orthometar isn't. For economy today, I think you are more likely to get a deal on a Nikkor than anything from Zeiss. The key is to be patient--Ebay usually has anything you want at an "aspirational" buy-it-now price, but most of these lenses will show up at more reasonable prices if you can wait.There is also a Zeiss Planar 35mm f3.5, and a Zeiss jenra orthometar 35mm
Both of these are harder to find, but may be less expensive.
The 3.5cm nikkor is also excellent.