How many do you need per 'product item'? Just add the cost to the final price?
Alibaba have them cheap if you can wait for the postage times, some places are showing M12 thumb screws as low as 1 cent as piece.
https://m.alibaba.com/product/60716...m=a2706.7843299.1998817009.104.34153176MF4Hnm
Can you not usestuds with wingnuts on the end ? or screw bolt through a wingnut wont look as nice but would work still
I usually weld some studding or a cut up bolt to the other bolt to get a cheap T handle
Its to stop a lenght of shs sliding inside another lenght of shs
I weld a nut on the outer piece and drill a hole through
Dont think i could get it to work with a wingnut but let me know if im being stupid would be a lot cheaper!