Gift ideas for a teacher?

Bob

Bring him a grilled cheese sandwich.

karly

A vape kit

Gypsyfish

I would go with something cute- if you look on Zazzle.com, you might find things with physics sayings or expressions. I know someone who has a t-shirt like that, and I think there are coffee mugs, too, which would be safer since you don't have to worry about size. Here's a link- https://www.zazzle.com/s/physics+mugs https://www.zazzle.com/woodchuck_physics_funny_tees_mugs_gifts_etc_postcard-239447656029788338