I looked through several tripod catalogs and found nothing like you want.

But I did find a number of flash Brackets that might work.

They attach between the camera and the pan head.

I suggest you go to www.porters.com and have them send you one of their 120 page catalogs.

I also suggest you visit a local camera store and see what they can come up with.
Not a department store camera department, but a camera store that only sells cameras.