Focusing Enlarger Lens?

I have inherited an old Italian enlarger that is called either an Industria Fototechnica or a Coldon Color S.C.. It has a Schneider 105 mm lens on it that is of good quality. I'd like to be able to also work with a smaller format and so need a 50 mm lens that will fit this enlarger. It seems to have a 45 mm thread size. The hitch is that this lens focuses like a camera lens. The enlarger doesn't have a bellows to move the lens closer and further from the negative to help with focusing. Everything is focused by the lens.

I've been asking around but have yet to get any help on where I might find such a lens now, what it's called, if only Schneider made them or if there could be a possible workaround like using an old screw mount camera lens.

Any help would be greatly appreciated!
Michael

In this age of digital imaging, darkroom equipment can be very inexpensive. It might be cheaper and easier to get a complete medium format and 35mm enlarger than to get a focusing lens for your present enlarger.

I'm inclined to agree with Jim; however, if you're intent on using your current enlarger, you might consider trying a camera bellows in conjunction with a conventional 50mm enlarger lens. You'll need adapters, too. Adapters to attach M39 lenses to M42 mounts are moderately common (many Eastern European eBay sellers have then, since the Soviets produced M39 SLRs, and the adapters could mount those lenses on later M42 SLRs). If it's truly a 45mm mount, though, you might need a custom adapter. Also, the bellows might add enough distance to make proper focusing at larger print sizes impossible -- and "larger" might mean "any," for all I know! All of which brings it back to Jim's point -- there are a lot of question marks along the path I've outlined, and you might spend as much going down that path as you would on a "new" (used) enlarger only to find that it won't work.