The one listed for '32-'36 roadsters is $125 plus the switch from Speedway, but you can get a generic one for $30 that has an integral switch on the back. It says "clamps", but I think that's a hole through the frame clamped with a nut on the outer shaft but I'm not sure - Roadster Windshield Wiper from Speedway Motors, America's Oldest Speed Shop