I rebuilt my own. Most were made by Ranco if its the original. Rebuild seal is still available.

http://www.ebay.com/itm/Mopar-1968-1969-Charger-Superbee-GTX-Heater-Control-Valve-Repair-Seal-/231074491766?hash=item35cd1ced76:m:m0qaL_ZwA2sEfMeVa608lbA&vxp=mtr

There is also this site:
http://www.heatercontrolvalve.com/