Like I said.. it's a common failure, they should..
edit.. just checked ********.. #20369894 $5.45ea, now I'm SURE they'll have them..
Just make sure you clean the 20 year old grease out of the rail that it slides in REAL well (and re-lube with fresh). If any of the other windows are slow to roll down it would be a good idea to do the same to those before you find out exactly how common the failure is.
