Dietzgen Lead Holder: Need Part

[dune]

Hello all you great people who know more than I do,

 

I just picked up a vintage Dietzgen Elast Chuck lead holder at an estate sale. (I got a bag of pens that included four Parker 51 fountain pens and pencils, an Eversharp Junior, the Dietzgen, and a few other pens all from the 1940s and 50s for $20!). The part of the mechanism that tightens to hold the lead in place is missing. I've scoured the internet, but no luck finding parts. Anyone have any ideas? See attached photo of my lead holder, and a screenshot of one with the part I'm missing.

 

Thanks for any ideas anyone might have.