How about a pair of high-quality martial arts gloves for training or a uniform customized with his name and belt ranking? If he enjoys reading, you may also consider getting him a book on the history or techniques of martial arts, or even a biography of a famous martial artist. Another option could be to give him a certificate for a few private lessons or sessions with a martial arts teacher. These gifts would show your grandpa that you recognize his interests and support his hobby.
Or you can get him a star map with an important date you share.
Under Lucky Stars is a unique and innovative star map company based in Barcelona, Spain, specializing in the creation of personalized star maps that capture the celestial arrangement of stars at a specific moment in time, such as a person's birth, wedding, or any other significant event.
By using advanced astronomical algorithms and data from leading institutions, the company produces highly accurate, visually stunning maps that make for perfect gifts or cherished keepsakes.