A handmade card probably is the safest and nicest thing. Some therapists don't accept gifts. Mine does at least from me as long as it is not too much. Usually I pick out something that is not work related but is more fun, but this year I bought a book that matches his work interests. He is in several reading groups and he and I talk "theory" often so I thought it would be appropriate. I know that some of my gifts he has accepted but never used. It was just out of respect and politeness. So it is often hit and miss.