HELP 21st BIRTHDAY GIFT!!?

my best friend (male) 21st birthday is here! i need a gift for him for under $40. he doesn't want alcohol (we drink that all the time anyway), his mom already got him a flask. hes a navy diver and loves that, and also enjoys fishing. HELP!! im at a loss. I thought about getting bar gles engraved with his last name..? I want to make it something memorable.