In addition to BM-12 mentioned previously, BM-17 proliferated too (the georgians for example had it during the last war), though whether it is actually worth using weapon slots to put it into the game is a different matter; BM-9/BM-12/BM-15 should be sufficiently representative for non USSR users during the Cold War period, at least in my opinion.
Sorting out the post cold war period is a messy proposition.
Not only more russian rounds have been cleared for export but a variety of countries now manufacture 125mm rounds based on indigenous designs and sell them each other. For example the israeli have made a 125mm APFSDS for export and have sold it to India (source
http://www.globalpolitician.com/2345-israel and confirmed by several others). I will see what I can dig out.
Only tangentially related but I have some notes on combat loads used by some countries on russian tanks, I can clean them a bit and post them if you are interested.