In the past I have used 9mm in Chinese 7.62 long mags and never had any feeding problems. But that's just in Chinese guns. Never tried any others.
Some Norinco 9mms came in with long mags that had fillers in the back and others had actual short mags with a filler in the mag well. If you do ever succeed in finding that 9mm barrel, look around and find some of the Norincos with the fillers in the mag if your Yugo mags don't work.