What would be wrong with a regular door knob?
Mine doesn't have one, just a loop-n-hasp with a spring clip.
After awwing over your little human chickie and his adorable ensemble...
...I gasped at
those latches, they frequently will lock someone in, I advise against them.
Course there
are two there with the dutch door so if only one fails, you'll be able to get out. This is what I use for my coop doors, oh and there's screen door spring for autoclose. More pics on
my coop page about half way down.