Found a supplier of the rubber base gaskets for the roof mounted aerial on ebay uk.

This is just the rubber sealing ring, not the whole base.

Generic seal for most models , not just the Mk4

Since they are coming from the UK, we'll save a heap on postage if we order them together.
Price is 2.95 UK pounds - cheap - plus postage.

dylan8 is ordering these, so send him a PM for numbers.
He is getting a postage price from the supplier as well.

here is the link to check it out;

http://cgi.ebay.co.uk/VW-Golf-Passat...04159004r10115