Here you go, found it at last! £12.50 inc postage:
http://cgi.ebay.co.uk/ws/eBayISAPI.d...m=230426137648

He also sells a "kit" for £29.50 which is the adapter with a pressure-switch banjo bolt, if you want to run it with brake lights for the road:
http://cgi.ebay.co.uk/ws/eBayISAPI.d...m=230426137632

HTH.

I fitted a Brembo RCS to my 996 recently with double banjo bolt - the existing brake hoses were fine however due to the position of the RCS brake line fitting (underneath the m/cyl) the head of the banjo bolt is very close to the fork leg - about 2mm clearance. I jiggled the standard bar around a bit but I may need to do a bit more jiggling.
Not sure about that e-bay adaptor - I wouldn't trust using an unknown make/material spec part on my brake system, but that's just my opinion.

I'm not using a double banjo, but I do use a pressure switch that probably has the same clearance issue. I put longer slightly bars on mine so I could move everything outwards down the bars to give better clearance. You probably wouldn't notice as they were less than an inch longer, but helped loads.