I recently purchased a SIG Pro 2340 40 Cal Slide assembly from a Texas based wholesaler for $119.99. It mounts and cycles just fine on my German Pro 2022. The slide and barrel were in great shape, night sights were dim, the magazine (blued) had a little wear and a couple spots of surface rust and it also came with some additional parts (breach block, trigger bar, slide release, magazine release, springs, pins, etc.) and a brand new (in bag) reduced reach trigger. The parts were pretty worn (sans trigger) but all appeared functional. I also picked up some parkerized magazines trade ins for $14.99 to go along with it. The magazines were also pretty worn in respect to finish but no rust and the followers were in good shape (probably will need new springs to be safe).
Anyway, if you are looking for a caliber change on your SIG Pro, this might not be a bad deal to consider. Now a hunt for a 357 SIG barrel to make it complete...