In order to buy him a present you have to know sieothmng about him. What he likes to wear, eat, watch read, listen to. If you don't know enough of that, just give him a gift card from Pennys, or some store. I think what he'll appreciate most is a note from you telling him that he was a good teacher and why. Teachers don't get much appreciation, and like the rest of us, they enjoy knowing someone thinks they did a good job.