Here’s a starter on UK Amazon; found by doing a Google image search from a US gaming forum.
Try searching on this image for other suppliers.
I’ve deliberately broken this link, as the forum tries to load it as a Kindle preview for some reason remove the ~ and the space either side.
http://www.amazon.co.uk ~ /Anti-Static-Aluminum-Cutting-Thickness-PNR5000/dp/B00VX74O38

For other ideas, and how to use the plastic wedges, see here
https://shop.sunhayato.co.jp/en/blogs/problem-solving/lead-bender
Bill