Heard that southbound trimmers on the UK south coast do the correct stuff. Obviously this is not cheap (approx £300-ish), and would cost a bit more to post.
Have bought the cabrio hood cover from them which was very good quality (worth the £325!!).
Might spring to them once the bodywork is done, and paid for.
Fellow (964 RS) owner seemed satisfied
http://www.porsche964.co.uk/rev_rep/reports/gs1.htm
Southbound Motor Trimmers
Little Dean Yard, London Road, Stockbridge, Hampshire, SO20 6EL, England
Tel: + 44 (0) 1264 810 080, Fax: + 44 (0) 1264 810 080
No connection by the way.