You have a couple of options. One is to buy a new PVC panel and simply re-sew in a new panel. Another is to glue a new section on. You can cut out the old panel leaving an edge to glue to. Then buy another PVC sheet and use PVC clear adhesive to bond the two together. Duct tape sticks to PVC pretty good, so you can also do that as well. The lightest option is to buy some ripstop nylon and replace the panel with lighter fabric. PVC is heavy.