79 tailgate window

[edgoodell@gmail.com]

I'm having a problem with the electric tailgate window catching on the latch mechanism bolts while it is going up or down. There is a spring loaded plastic wheel which appears to be installed to alleviate that from happening but the spring on mine is broken and nonfunctional. Does anyone have any ideas about where I can buy a replacement unit (or the spring)? The spring looks like a 'parts peculiar' for this application.