I recently went through the same thing looking for lenses for my
R-D1 (think Bessa R2 body with the viewfinder from the R3M and the same 6MP Sony CCD as the Nikon D70). I ended up watching Ebay, KEH, Adorama and Igor's for nearly a month until I paid $320 for a lovely little (tiny even)
Canon 28mm f/3.5 from Adorama. The lens seems to perform quite well given it's age, but these don't seem to pop up very often unfortunately. Rangefinder lenses are just not inexpensive in the least.
I've heard of people using the Industar-69 on the R-D1 (whose APS-C sensor is roughly half-frame) but I do not believe it would cover the full 35mm frame. Additionally, while the lens is in M39 mount, the register distance is significantly shorter than the standard 28.8mm so will require modification to focus at all and will not offer rangefinder coupling.
Really, the only 28mm lens in M39 that consistently sells for under ~600-800$ is the Soviet
Orion-15 which shows up on Ebay somewhat regularly for usually under 300$. The speed is only f/6 but the lens formula is a simple and classic symmetrical Topogon-derivative which ought to provide quite good image quality even wide-open and no distortion to speak of.
Another option is to scrounge the internet for phone numbers of small camera stores and dealers and ask around. Sometimes smaller stores (like The Camera Trader) will have unique equipment for well-below market price. The Denver Photographic Society's swapmeet on May 6 at Jeffco Fairgrounds may yield something as well!