Thank you, robali123!
I used regular PLA plastic which is also used in the production of disposable tableware and such. Of course, this plastic is not as strong as metal, not even close. And yes, it is quite brittle, you can probably break the thing by overtightening the screw. So I would not recommend you throwing away your metal tools and replacing them with plastic ones just yet LOL But it is strong enough to hold this lamp securely on any surface in any orientation, so at least it is good for something :-)