Three Monkeys, Three Typewriters, Two Days

your first step should be: buy a bilingual keyboard, they are not that much more expensive (asking in russian bookshops did the trick here in berlin)

I considered that. For the amount of use this is likely to see, it's not worth it. Plus I like the feel of my keyboard, and I'm not willing to risk the return of wrist issues from using keyboards that don't quite feel right... So buying a keyboard would be a much larger investment of time than I can make right now. :(

X does have a transliterated layout, but it's a variant of the
general "ru" one. Try setxkbmap ru phonetic. (There is also
the ru_yawerty, but it doesn't actually seem to work.)

My XFree86 4.0.1 install certainly has no Russian layout other than "ru"... (I did look at all the keyboard layout definition files before doing any real work...)