Photog dopers: 72mm Ringflash or alternative??

I have searched and searched and I can’t find a not-bloody-expensive ringflash that goes as high as 72mm for the fitting. My macro lens is 72mm [edit - 82mm] and the whole point of it being a macro lens is the ability to take pictures of things while they are very close to the lens (like one or two centimetres away from the glass) but the obvious problem is that the lens obscures the flash at that distance.

So I would like either…

A not to expensive (£200-£300) ringlfash that will fit a 72mm [edit - 82mm] lens without reducing the effective area photographed (by having the ‘hole’ physically smaller than the lens)

or…

something designed to solve the problem that is not necesarily a ringflash (like for example the thing Dexter has which appears to be two flashguns attached either side of the end of the lens)
So do you have any recommendations?

eta: If you need this info - my camera is an EOS 30d. And if my search has been correct, it’s not 72mm it’s 82mm http://www.amazon.co.uk/Sigma-24-70mm-F2-8-Macro-Canon/dp/B0009E1XF8/ref=sr_1_8?ie=UTF8&s=electronics&qid=1262381686&sr=8-8

(I don’t have the camera with me so I can’t confirm)

Dang, 82mm is big.

Bower makes this ring light that has an 82mm adaptor.

On second thoughts, it might be 72mm afterall…

I’ll be able to confirm when I get home.