My parents got me my first cap from the US when I was 12 years old. His dedication and interest in his hobby is praiseworthy. He has made it a habit to read history books that give him historical significance of the caps he possesses. He is also in the process of compiling a book on his remarkable collection. For starters, ask your friends to give you all the caps that they can.
Old people can be very useful in getting old caps.
Ask your family and friends to look out for unusual caps whenever they go out of the city. Read historical books, and if you find any unusual cap, get a replica made. If you are informed that a cap is available somewhere, go and get it. Advertise your interest on the Net and see if anyone can engage in a barter with you. For birthdays and festivals, ask people to gift you caps instead of anything else.