1957 Hehr Front window assembly - Lost screws and tube nuts

Hi,

I have been working on my front window assembly from my 57 Westerner. I have lost two important screws. Can’t find em.

In the assembly, it has a clutch head screw that screws into what I will just call a tube but for lack of the correct term. It looks like this.





It’s in this part of the window frame.





Here is the tube nut installed from the back.




Installed as a pair it looks like this.
The screw would tighten "over" the duel frame window assembly to help keep it in place.



The left duel window assembly sits on top of the main back frame and is attached with two of these screw nut pairs. I have lost one of the tube nuts and two of the screws. Anyone know where I can get something to replace them or at least tell me the correct name of the tube nut?

Thanks,

Rod