I've been using the household opal (not frosted) bulbs all the time, and with great results. The special enlarger lamps were never made in the USSR. The most important point is to use the bulb with no visible defects un glass and opal layers, an to use onlu the power your enlarger is rated for - I thnk it's 100W for you Opemus, check it on the nameplate somewhere. If the lamp is more powerful than recomended, it may overheat and damage the bulb socket - of course, if it's not a porcelain one like in my old faithful Magnifax II

Cheers, Zhenya