scooter, I don't think there are any current aftermarket units that self cancel, get used to it
the cancel function is mechanical, not electrical, and is only present on some vintage units that have a small rubber wheel on them that rides on the steering wheel
Bill
The original poster's truck is a 1954, so there are reproduction signal units that almost match the GM accessory signal unit for that year. It is self-cancelling (without the rubber wheel used on GM accessory self-cancelling units for earlier years). The price of the reproduction parts is $$, compared to other after-market non-cancelling units.
Turnsignal cup assembly Turnsignal switch cancellor Turnsignal handle (not like original style, but close)
As is the case with any signal assembly/installation, a flasher module and holder (and wiring, and patience/perseverance) would be needed.
Chevs of the 40s sells a nice electronic flasher (it works with incandescence and LED signal lights).
flasher bracket (3-prong like original - 2-prong brackets/flashers are also available)
6v flasher 12v flasher 12v LED-compatible flasher 6v audible flasher 
