Our customer service department (800-845-3567) has the name and number for a company that can sell you the right zippers and matching fabric. (B&D or something I think, but I can't remember). They can also sell replacement panels for most tops, but it's not a cheap option.
Zippers are frequently repairable, so I'd agree with the local boat canvas shop idea.
Of course, I REALLY like Alstjruby's idea of just buying a new one, too.
And, I just realized that you didn't actually say it was from Bestop. How arrogant is that? If the top is ours or from the factory we can help.