i think tvt is the only co. offering this service. its in another thread and they say its not something they want to do on a regular basis due to the current workload they have.
i would recommend if you are going to size down your oem pulley research first HOW much you will want turned down. millimeters make a big diff. here as the s/c is spinning at a huge rpm.if im correct oem is 72mm c3 midsize is 69mm and c3 s/c pulley is 65mm. also a bearing swap should be considered as when i took my oem off at 40k i found sizeable bearing wear on the s/c pulley AND on the idler puller. also the tensioner pulley shows some wear and is being replaced just as a precaution