Have spotted G4 canoe mountings on eBay fits RR RRS and Disco3 - no mention of FLitem number is 380302815123 just in case link below doesn't work.
http://cgi.ebay.co.uk/Land-rover-kayak-canoe-surf-water-craft-carrier-kit-G4-/380302815123?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item588bd06f93