replace missing track rail


Hey all, i have a 6ft bed taco, the previous owner removed the passenger side track rail from the side the bed liner. I understand that the tonneau cover clamps to this rail. Not the header or the tailgate one, but the rail that comes pre installed on both sides of the bed liner. Sorry for being so discrptive, I'm not sure what the name of this rail is actually called. Yoy guys have been very helpful, thank you.
I think this is called a bed deck rail system. Toyota has them for the 5' short bed, and 6' long tacoma bed. I too have the 6' system in my access cab. Idk if one can buy individual rails.