Everyone seems to share this problem, the air conditioner filter vent cover breaks. A trip to the local RV supply will cost around $25 for filter and cover. I solved the breaking tabs problem with some neodymium magnets from Harbor Freight.
At the end if the frame there are a couple of screws. Stick a magnet to the screw. Put a drop of super glue on each corner where the magnet is and pop the cover on, using more magnets as clamps. I went ahead and glued them to the cover as well.
I also picked up a $3 piece of foam from Ace Hardware that made me 3 filters. Not bad for about seven bucks.