Replace v-brakes with rim caliper brakes with no center hole: adapter? - Bicycles Stack Exchange
U-Brake Service | Park Tool
conversion - Is there any kind of adapter to mount v-brakes or cantilevers to a frame that's not designed to accommodate them? - Bicycles Stack Exchange
Woodman V-Brake Adaptor - WebCyclery & WebSkis | Bend, OR
Identiti Rebate Fork Brake Mounts V Brake Adaptors
Wanted: U-brake to V-brake Adapter Plate | Motored Bikes | Motorized Bicycle Forum