Hi Adam
I guess the PO fitted the central front beam clamp as added piece of mind to ensure the top did not detach in the unlikely event of the rear clamps becoming undone, sorry my clamps are not for sale as they are needed for my car. Finding genuine Jaguar Clamps is almost impossible as I have searched everywhere i can think of to find a pair without success. RS Components sell a very similar clamp to the Jag original but differs at the connecting point and is similar to the ones fitted to your hardtop attaching to the C-pillar with a hook arrangement as apposed to a hole/bolt through set up. Good Luck in getting sorted with something that works
Brian