In case you have trouble sourcing the buttonhole elastic for the RC3 face shields, as I have, you could try a plain elastic adaptor such as https://www.thingiverse.com/thing:4310197 or print the whole thing in PETG (I do not thing PLA would work, being too stiff). It is not wonderful, being non-adjustable, but could easily be made in a variety of sizes. It is disinfectable though, unlike the elastic, and it definitely does not contain latex.

Prusa

I3 MK3S

No

No

0.2mm

20%