PVA usually does the trick, especially if you have some "grooves" or similar to slot the panes into. Some "general purpose" glues like UHU (standard yellow tube) work as well. Just steer clear of CA glues, as they tend to fog up any clear plastic, especially if not properly ventilated during curing. A year ago, I actually bought a specific canopy glue, but that one doesn't really have that much benefit - just use PVA sparingly and make sure you can fix the parts in place properly.