I agree about the "monster Tessar" solution, if you don't mind the bulk. I have a 375/4.5 Orbit lens of that description, and it makes a nice-looking image as long as you don't mind working with its size. (You cannot appreciate how big an Acme #5 shutter is until you've held one!) I don't remember how much I paid for it, but it wasn't much. There's probably a Paragon version of the same lens, though I think the f/6.3 version is more typical.
There are quite a few miscellaneous Tessars out there, but it's hard to find them reliably. I think you just have to keep checking on the usual sources like KEH and eBay.