I had the same problem on my two 95 builds, I took them both to my dealer who said they couldn't get the small part any more but offerred to clean the guides for me..."they get filled with gunk..' after getting that done some of the smaller windscreen replacement guys over here offer a 'buffing' service for badly scratched glass..using a drill with a pad on it with a 'jewelers rouge type' polish buffed the scratches for about 15 mins [each]with constant fine mist spraying with water [keeps heat down from buffing and not to let dry when buffing] and reapplications of the polish...deep scratches ..if you can feel them with your finger nail runs over them generally won't buff out completely but depending on how bad they are you may be able to get a decent result... on slight scrathing the window looks perfect a slight trace can be seen when the window is wet/dirty [rain] as water beads along where the window has been buffed...heavier scaratches when window is clean you may see some lines in daylight..[one of my cars was quite bad..its not 100% ..it was obviously scratched ..now ..well I'd give it 80-90%..
The window guy also suggested as our cars [and others ] are prown to this ...when you wash your car ...with your finger pry open the rubber window seal [where the outer frame is passed by the seal ...either end] and with your soapy sponge follow behind your finger washing along the inside of the seal and the glass.....then when rinsing again open the seal running your finger along with the water behind rinse down and along inside the seal [not blast].. depending on how grubby they are you might be surprised as I was with dirty water that flushes back up [after the first go]...
I was very tentative about using the windows after realising how the scratching occurs etc. but now after having the guides cleaned and routine window/seal washing I use them regularly and so far so good several months later.
Dave