I think CJPonyparts still has some of the NOS Ford Carlite coupe quarter windows for sale. There was a limited run of these a few years back and I think everyone has sold out of them but CJ appears to still have some... and $630 for the pair is not bad for new.
http://www.cjponyparts.com/ford-quarter-window--with-'mustang'-script-coupe-1987-1993/p/FBQW3L/
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