I like the suggestion from the Dinosaur Comic below, and, may I suggest, if you’d like to celebrate twice a year, that you look into Mole Day?
I am a tremendous fan, and dressed up as a knight errant serving mathematics for some Halloween in high school. All that’s really needed for a knight’s costume is a tunic, tights, a belt, and a sword. Sadly, I can’t find any photos of my math sword, which had two steel rulers for a blade and a protractor for the crossguard.
Teenaged me wishes you a very happy holiday and is kind of baffled that old me spends this much time talking about religion.