I haven't tested this to see if it includes Cyrillic input, but you could try the AllLang OS (9700AllLang_PBr5.0.0_rel541_PL5.1.0.96_A5.0.0.344 _Telus_Mobility.exe) from Teleus Mobility.
To give this a go, download and run run the 9700 software from this page:
https://www.blackberry.com/Downloads...E607FE7CC0E1A0
Delete this file:
c:\program files\common files\research in motion\apploader\vendor.xml
Connect your Blackbery and run this file:
c:\program files\common files\research in motion\apploader\loader.exe
You'll be able to see which languages are available for install when you go through the installation wizard. Installation takes a while and includes a couple of reboots. Dont' disconnect the device until it's finished.