Depending on where you want the various symbols, you might find a custom set of keycaps that match what you need for the ErgoDox.

They will cost a lot more than you expect (low volume manufacturing).

This is one example, plus others others in the same subreddit: https://www.reddit.com/r/MechGroupBuys/comments/iks5r5/gb_ka...

Personally, I bought a set with a few daft symbols, as I can easily remember that the biohazard symbol is Ctrl, and it gave a bit more flexibility.