Ideally you want an original or repro blinker switch and wire cover for a 1957 VW Beetle. This is a "bolt-on" for the column that you currently have in your car. This switch is nearly identical to that used in the original Speedsters, and will require a floor mounted hi/lo beam switch.
If you want even MORE authenticity, use the column and column mounting bracket/gasket from the same car. The column tube comes with the horn brush attached.
If you want the the hi/lo beam switch as part of the blinker, use the Beetle housing and wire cover and the internal electrics from the 1966/67 VW Bus. The Bus arm looks nearly identical to the blinker switch arm from the 356C and the Beetle housing looks identical to the 356A so you're car will have a nice Porsche look to the whole assembly.
Should you decide to use the VW Bus electrics, you MAY have to open up the slot in the housing to accept the thicker blinker arm, this will depend upon the after-marker manufacturer of the housing. No matter . . . this is an easy Dremel job. I'll do it for you if you like.
Honestly, if you feel uncomfortable with the whole process, I'll swap out the internals, enlarge the opening, and paint it up for you, no problem at all.
I'm not trying to push you in any direction, just make things easier for you. The VW Beetle assembly is a bolt-on, the VW Bus assembly requires much more work to achieve the same "look." The only difference between the two is essentially the hi/lo option built into the Bus electrics which, as I said, can be placed within the Beetle housing. Keeping the results as a bolt-on rather than a bit of a chore.
"First get a 3 ft piece of 2 inch exhaust pipe and slice it down one side to make it the correct diameter then Mig wield it back together . "
Using the Bus switch and Bus column tube set-up is along the lines of Donald Sutherland (Oddball) sliding the larger pipe over the smaller gun barrel on his tank in KELLY'S HEROS. Way too much silliness for just a "look." May as well do it correctly by using both the switch and column tube from a Beetle.
Luck !!
FoRUm TUrd