If the screws are loose, take a wood toothpick or wood matchstick. Remove the screw then put a drop of super glue on the end of the toothpick or matchstick (not the end that you light on the matchstick!) and push it into the screw hole. Let the super glue dry then reinstall the screw. Or, get longer screws provided they don't go through the plywood.
Can't help where to get the replacement latch, although, Camping World might carry them.
2015 Forester 2301 - Chevy
Skip & Deb - Denmark, ME & Delray Beach, FL