not sure if you would like the aesthetic but the parlee carbon one comes in the size you are looking for and spreads the clamping force over a wider area. A little blob of carbon assembly compound generates all the friction it needs to never move.
the last part of the Cielo puzzle was a braze-on adaptor. The Shimano band-on front mech is a 28.6-31.8 which unnerved me a bit so I went for an aftermarket adaptor at a true 28.6
http://www.parleecycles.com/store/
not sure if you would like the aesthetic but the parlee carbon one comes in the size you are looking for and spreads the clamping force over a wider area. A little blob of carbon assembly compound generates all the friction it needs to never move.