The whle kit and kaboodle (belt plus retractor) is still available from
VW.  Well under $100 IIRC.  Since the nylon belts can't get any better
over time, why not fix the problem and upgrade your safety at the same
time?

I did the rear shoulder belt conversion and added belts for the
PO-installed rear-facing seats.  Now I just need to take my own advice
and do the fronts to have completely replaced the belts.  (OK, I left
the original rear center lap belt).

ed