A tailor is the easiest solution and well worth the $10-20 cost. You can even have them put in a different type of zipper; I like the two-way zippers in my skating jackets so I can unzip the lower part to demonstrate hip crease and position.
If the zipper pull itself broke, fabric stores like JoAnn and Hancock sell replacement pull kits. I've salvaged many jackets and a few sport bags. The kit comes with an assortment of pulls and instructions on how to remove the old one and put on a new one. For $4, it's worth a try.
One of my friend's mothers is a former professional seamstress. She had a jacket with a broken zipper, so she just trimmed off the zipper entirely and installed snaps down the front. It looked really sharp. She said the zipper was cumbersome for the car anyway.