How about rigging one of these up?
http://www.lowes.com/pd_148368-37672-881688_4294711029__?productId=3013915&Ns=p_product_qty_sales_dollar|1&pl=1¤tURL=%3FNs%3Dp_product_qty_sales_dollar%7C1&facetInfo=
It'll hold the door flush like it's latched, but just push in on it and it'll pop out. You might have to remove the spring on the door, though.