use a mil spec switch(MS 27734-23)it works fine. you can find them on eBay on off (on). I gave the solution to Hansolo and he posted it for all in his thread where RK found it
Fuel Panel RCVR Knob added to my Shapeways site available in gray white and polished white
https://www.shapeways.com/product/HUMX68C2T/rcvr-knob?optionId=179379285&li=shops