Assuming you mean the belts with the metal faceplate glued on to them, the good news is that they seem to have been used on a few models in '66. (Although they may be less common than the basic belts that had the GM letters molded into the plastic. Personally I prefer the basic belts as they seem to survive a little better.)
At one point our sponsor TinMan (Dave) had some of these. You might want to try there...