I have 1 of those critter nation cages and I just got a new cage that I love. It's a lot more convenient for feeding than the giant doors on the critter nation cage if I don't have time to gather them in again.
That's where I found it. It's not quite as wide as the critter nation cage, but only by about 3-4".
All the feeder doors are guillotine style, BUT they have to snap up or down. So your birds definitely can't lift them.