A rather belated reply, but I found this freely downloadable font works for Altium:
http://all-free-download.com/font/vario … nload.html
It’s called Hazard and it has a variety of hazard symbols.
The one I wanted was the electrical hazard symbol, the lightning bolt in a triangle, which “F” in this font.
I hope this helps someone who was searching like me and found this forum.