Official dealers;
http://www.bobsknobs.com/dealers/dea...liadealer.html
You can also try
https://www.telescopes-astronomy.com...umb-screws.htm but call for price and availability first as web site may not be up to date as it was last updated mid 2020.
I would think you could order direct but local suppliers may have what you want on their shelf. Not sure if Bob’s Knobs ship direct to you. Make sure you get correct one for your telescope as there are a few different ones but clearly stated on the Bob’s Knobs web site.