http://www.ebay.co.uk/itm/Shimano-SM-AD17-Front-Derailleur-Clamp-Band-Shim-Adaptor-Reduce-34-9mm-to-28-6mm-/350584164224
or I've used rubber shims from light brackets before if you want to be cheap
@fredtc started
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http://www.ebay.co.uk/itm/Shimano-SM-AD17-Front-Derailleur-Clamp-Band-Shim-Adaptor-Reduce-34-9mm-to-28-6mm-/350584164224
or I've used rubber shims from light brackets before if you want to be cheap