I have a Patagonia Jacket (hemp) and the zipper is messed up.

I have the Hemp Canvas Ranch Jacket. I love it. But the zipper refuses to stay closed after several years of use. I zip it up, look down, and the zipper will have opened up below the “pull”. I guess I need to replace the zipper, but I am not worth a hoot with a needle and thread. Where do I get a zipper and is there a special place to do it, or would any seamstress (I don’t know the gender neutral term for that, sorry!) be able to handle it?