If you upgrade your desktop manager to 4.3 you should be able to get it. I found info on the Blackberry Technical Knowledge Base that said it was supported. Here's the article number: KB14321.
Once you have the multi-language DM installed, connect your device and run app loader. Put a check mark in the box next to the language support for Russian and you should be all set!
I take it since no Russian there's even a smaller chance of there being Serbian? Or even Croatian? They are close enough. (non cyrillic is fine too)
Multitap mode takes forever