[lunarhighway]

duck tape or similar will work, also staples can be used, depending on the sort of bond you want.

most general purpose glues that are suitable for plastic should work fairly well.

just make sure the parts overlap or there's a third trip on the back if you want a fluch fit.
if you really want to be sure punch trough some staples and cover the seem with some tape... if that comes loose you'll probably want to use a slingle piece or another material