What broke exactly? I broke mine as well, it's 6/5/4 front-zipper. Haven't unzipped it all the way and upon removing the suit teeth stripped on one side. I was looking to repair it, but at the end it works just fine.
At the end of the zipper, were its supposed to stay together when you have the suit unzipped all the way.
Sounds like exactly like mine!
You don't really have to fix it, just work it in every time you'll be zipping up. Mine has been this way for 2 seasons now without any issues. But even if you really wont to fix it - your best bet is diving shops.