Did the thumb screws for your optical posts go missing?  Well, this is your lucky day!!  Working replacement screws are available.  They are plastic and will not scratch posts.  Will fit Newport VPH#, Thorlabs PH#, and one of the screws for Newport VPT# along with other posts accommodating 1/4-20 Thread.  Yes, they may be translucent white but a color Sharpie can do wonders!!

(5 for $5) Thumb Screws (Thumbscrew) for Newport, Thorlabs, Etc. 1/2" Post Holders

 0.5 in. Length, 1/4-20 Thread