Interesting fix, but those white plastic 'slides' are readily available from the dealer, about $24.00CDN a pair. For my 85 380SE they were part no 126 720 01 42. Probably on many aftermarket shelves as well, and cheaper. Fastlane here calls them "Window Regulator Roller Sliding Jaw", Febi $6.96.
There are several threads here on installing them. I found the easiest way to peen the rivet (supplied) onto the regulator arm is with a socket same diameter as the rivet, used under the piece, on an anvil while you strike the head.

__________________
1986 560SL
2002 Toyota Camry
1993 Lexus