Just installed a new gray three windowed pop top canvas on our faux
Weekender (1980 Westfalia pop top and roof skin grafted onto a 1991 Carat).
After a few uses, the right side window vertical zipper failed (separated)
due to an inadequate zipper stop at the upper end. Searched around on the
internet and found "Fixnzip", basically an adjustable zipper slider with a
spring loaded screw that you can loosen and then tighten to clamp together
over the separated zipper teeth rows and bring them back together. Worked
like a champ, and as they suggest, one could just keep it in place as a
replacement slider, but we were able to zip it right off the end with the
zipper rows closed, and then painstakingly reinsert the original slider
back down. My wife then sewed proper stops on the ends so that the original
zipper won't repeat that trick.

I'm keeping one of these in the glove box. Medium graphite was just the
ticket if we had been unsuccessful in reusing the original.

Cheers,

Dave Milo