Similarly, I replaced the cheap-ass BSO-stylee thing on my Streetmachine with a Fox air thing after the former progressively lost all its damping.
Had to do a fair bit of digging to obtain a one in the right size, thobut. The spoingy mudbikes seem to have standardised on slightly longer ones. I dare say I could have emailed those lovely people at HPVelotechnik, who would have supplied me with something appropriate in exchange for a depressingly large bank transfer.