Check out
http://www.deepellumautoglass.com/ They have always been helpful for me on older glass. I had some similar issues with stiff gaskets and glass that wasn't right. They knew what I needed and fixed me up on the glass. I didn't ask about the gasket, I was just too ignorant at the time to know that wasn't how it was supposed to be. I haven't used them for my square, but they know their stuff.