You could probably send it back to Galco and get it replaced. Otherwise, soak it in water, wrap a baggy around your Glock mag and mold it to fit.

I don't like Fobus products personally. Cheaply made and I've seen cracks develop in the plastic.

If you're really worried about the area, Galls or Zahal will be happy to sell you some soft body armor. It's easy to tuck a spare gun under the arm attached to the panel carrier.