I recently acquired a used Shimano BB-UN72 bottom bracket 68x110 from a used parts bin at a bike co-op. Interestingly, the fixed flange is on the non-drive (left) side as opposed to the the drive side which is the norm in my experience. Unfortunately, I do not have the removable sleeve for the drive side with left-hand threading but would like to acquire one so I can use the BB. Is anyone familiar with this type BB? The only reference to such a BB that I could find is on the Park tool website. Further, are removable sleeves with left-hand threading available anywhere? Thanks.