I'd actually go to one of the UK as the US mats are designed for LHD!
928 floor mats are not symmetrical.
Try the following links ..
and look for ID968947330031 928 FLOOR MATS 4PCS BLACK (PORSCHE)
TEXT RHD CARS £ 49.00p + VAT
Have 928 mats available if you follow the ordering link...
Grab a UK Porsche magazine like '911 & Porsche' or 'GT' and there
are lots of ads. The Feb '03 edition of 911 and Porsche has an article
on the 928GT and also has an ad for Southbound Motor Trimmers (no
website) who have OE carpet sets for 928s advertised .. Good Luck.
Mark E. '90 GT