I suggest you take it to a hardware store and ask one of the handymen working there if he could fix it. Or perhaps an auto parts store. Those two places are your most likely places to find someone who can fix it for you. And probably neither would charge you anything to fix it.
Another possibility is to go to a fancy hotel which provides umbrellas to the guests. The porter may be able to fix your umbrella. If you do this, you should tip the porter for fixing your umbrella.
However, if you have to pay to get it fixed, it will probably cost you more than to simply purchase a new one.