buffman beat me to it. Both my '94 and '96 Impalas have the pink "hot dog" slide/guides, and while they are still available, the real solution is to install the white delrin/nylon rollers. Impala/Caprice regulator channels are also crimped to keep the "hot dogs" in place, but they are fairly easy to open up to remove the broken halves of the plastic.
The rollers aren't as cheap as you might expect. I paid over $5 apiece for the replacements at the dealership.