hi just an update for anyone who has come across this i got the laser from this ebay link
DVD Laser Head Lasereinheit in BMW DVD-M3.5,VW RNS-510 on eBay (end time 20-Jul-09 01:09:46 BST) that laser is for the mk4 also but the later ones ive found
so they do a DVD M3 and a DVD M3.5 and altho the laser itself looks very similar the ribbon is much thinner this is also the black cap one.