Update about my Valoy enlarger: I got (again for free) an old soviet 50mm Industar 96U-1 lens. Also I bought a set of M39 extension tubes from Aliexpress, dirty cheap! They're brand new, made from machined aluminum. The set includes three tubes, 7mm, 14mm and 28mm. I tested all three lenses I have now (Rodenstock Rogonar, Nikkor L 2.8 and Industar) and all of them work perfectly now!!!!!!!!! I used the middle tube, No2, the 14mm one. This tube is roughly (give or take few mm's) similar to the original DOORX Leitz tube. So I think that with this set of tubes, using in our case only the 14mm one, it will work also for Valoy II enlarger and with some adjustment for the autofocus function, with Focomat Ic. There's also a similar soviet 3 tubes set sold mainly by Ukranian sellers at ebay, with slightly different tube lengths, which I guess it will work just fine as well. I bought also a used Marumi focus finder (a very similar design to the well known Patterson one) and the film grain when focused is sharp and well defined. Especially Nikkor lens (and this I guess is not surprising) gave the finest and sharpest grain focusing of all three (Rogonar is just fine, but not as sharp as Nikkor and Industar is a bit on the soft side, but not bad at all).
Here's the Aliexpress link for the M39 extension tubes: