Single pivot brake with handlebar levers (Resurrecting an old Colnago)
There are interrupter levers such as the Tektro RL720 pictured here (courtesy of Rivendel):


You will need to redo the cabling, but standard V-brake levers will not work for a variety of reasons (handle bar diameter (conceivably, you could shim it on, but this doesn't seem very safe) and amount of cable pull (which you could solve with a travel agent, but this is pricey). Most of these are designed for 24mm clamp diameter bars, so you may need a new bar if yours doesnt have this diameter.

Arne's suggestion is a good one though - you could fetch a pretty penny for that thing from a vintage bike nut, and get something thats more discrete for riding around town and other things (and has the essential rack and fender mounts).