Brittle and cracked lower windscreen rubber trim

Hi, a couple of C3s we've looked at had the rubber trim across the bottom of the screen really badly perished, bits snap off if you touch them,,I found a post about this and if Im right I understand that these are just trims which are bonded to the plastic covers that close off the area where the windscreen wiper mechanism lurks, is this correct and if so has anyone effected a repair apart from just replacing the covers,,and if not are they very expensive?
Steve.

Just a quick followup, typing lower windscreen trim into the internet throws up ebay adverts for self adhesive trim which looks like it could be a possible fix,,has anyone used anything like this? it appears that many cars now use such trims, perhaps because of them having bonded screens.
Steve.