The early Super Sports(65-67) came with down tube shifters. They were made by Huret. Big and clunky.

Both Shimano & SunTour made clamp on types that should work. Try a bike co-op for used parts. The early Shimano 333 are reminiscent of Campagnolo for less $$. I put these SunTour ratcheting shifters on my Raleigh Super Course and have had them on other bikes. Don