We finally found the place to buy Lego in Bishkek. When we lived there 6 years ago there was one store that sold a few, but now lots of places sell some. But there's one place that's really the Lego place. And since it was a little hard to find out about (I suppose that expats with kids in Bishkek might all know and tell each other) (we couldn't find much when I searched online in English, but I found this place when I searched in Russian), I wanted to post it here.
Anyway. It's on the northwest corner of Soviet and Moscow. There's a fountain in front of the building and a poster with the Lego symbol on it. They have a pretty good selection and the prices aren't unreasonable. We had some very happy boys after visiting there.