We were there 10 days ago, and took our own skis but my sister and husband hired them from the ski hire place in the basement of Hotel Lodge, its just to the right of the Gondola, down some steps. They were really pleased with their skis and the service, not sure what they paid, but similar prices to other places. By the way the skiing was really good, great snow, we had a lot of fun! Have a good trip!
As Gerry suggested, Hunters are in the Flora complex and have one or two other depots around Borovets, one almost next door to Bobby's Bar. I have used them the past two years and found their service to be very good. Happy to change equipment if not satisfactory etc. They have equipment for those that can't ski that well but also some stuff for those that can. Prices? very comparable
I can only recommend the guys at Hunters as we've not used anyone else. 100% happy with them so well worth checking out if you want to compare two or three.