YEs been loking into them for a while now, can be bought out of usA, BUT HAVE GIVEN A PROTOYPRE TO pETE hOEY AND HE IS LOOKING INTO BUILDING SOME.
there are a few differant versions out there but they all work on the flat bar and hinged rod set up, if your not into details you can make one yourself out of steel , the money costs in these is the alloy versions, the only other problem is the provision to fit a sprocket cover to make it racing legal, but there is a work around and a mounting cover can be made to still get the clearance.