You can mix and match with Bert's, Traxstech, Cisco, Cannon and maybe others... Not sure if you are looking to buy tracks or just accessories to fit existing tracks, but I would highly recommend Cisco brand products. I've been outfitting my boat with Cisco tracks, and a few of their inserts, and couldn't be more impressed with the quality of the product and the service...
http://www.ciscofishingsystemsltd.com/
I also found that this link sells Cisco and Traxstech products slightly cheaper than other places - http://www.bigpapasportfishing.com/products.htm
Ken