We visited last year and went on the skidoo experience booked through the tour operator.
If you want to hire one yourself, not sure how that works, but thes guys who did the skidoo experience were always around the Rila Hotel - Maybe one of these can help you with that.
When we had a play on them a few years back, we booked through our instructor, got a better deal then then you would booking through your rep! Our ski instructor made a call for us and got us booked that same day, sorry cant remember the price - but a good crack. But if you have lessions worth a try anyway, hope that helps
just came back from boro had a fantastic time the skidoos are 140 lev per machine or 70 lev each expensive but well worth the experience go after dark asit realy enhances the experience going thru the forest