I used United Pacific turn signal clamp-on purchased from Summit Racing. Part number UPD-5007R for $31.99. It also required a 6 volt flasher part number UPD-110252 for $12.99. Easy to follow directions for wiring with my positive ground. Simply tighten the band clamp on the steering column. Well constructed and fit my 1932 column shaft.
I ended up swapping out the internal indicator flash bulb to a 6 volt equivalent so I could see the light. Since it doesn't have any self-cancelling cam, I also installed a stock GM headlight buzzer to remind me wired to the flasher...
https://www.summitracing.com/parts/upd-5007r
https://www.summitracing.com/parts/upd-110252