1. If you are close to your father like a friend, and know all his likes and wants, then just buy him one.
2. Or you can ask your father in disguise what he wants and needs recently. It is best to ask in advance to avoid being too obvious.
3. Being a teacher is very hard every day. You have to teach and use your brain all day long, which is very stressful for many years. First of all, you can start with his sleep. You can buy him a sun jar, which helps him fall asleep quickly and ensures the quality of sleep. You can also buy some nutritional supplements, such as brain and body supplements. If your father smokes, you can give him something to quit smoking, and filters are also sold.
4. Then you can buy your father a pillow or bed that helps him sleep. There are many health products related to these, and they can be searched in online supermarkets.