i saw this one on ebay:
http://www.ebay.com/itm/Glidetrack-SD-30-in-75-meters-Comes-Tripod-Head-Adapter-/300654004707?pt=LH_DefaultDomain_0&hash=item46006009e3#ht_549wt_1396
seems like a great deal to me? but i was wondering if there is something better for the same price or around the same price..