Localized keyboards are most commonly available from Apple for portable, rather than desktop, models.
Generally, the following nations are supported: Belgium, Denmark, France, Hungary, Icelandic, Israel, Italy, Japan, Korea, Netherlands, Norway, Poland, Portugal, Romania, Russia, Slovakia, Spain, Sweden, Switzerland, Taiwan, Thailand and Turkey
The correct prefix for a localized Apple part for a Russian language keyboard would be RS. For example, a localized Russian keyboard for an iBook G4 12 inch model is designated RS922-6901.
I see no evidence that there is any Russian version of the standard keyboards available with most desktop models, in answer to your original question.