This is an over engineered self closing latch I designed for my dart frog enclosure. The bottom latch would fall open sometimes so I replaced it with one with springs so it stays closed. There isn't a lot of travel in the springs so there isn't a lot of travel in the latch but it's enough to keep my frogs in. This would also be useful for other doors that you don't want to put holes in. The thickness of the base plate just needs to be adjusted to fit your specific needs. I've included a link to the springs I used since they had the most travel at this size.

uxcell Compression Spring,304 Stainless Steel,4mm OD,0.4mm Wire Size,8mm Compressed Length,15mm Free Length,5.3N Load Capacity,Silver Tone,10Pcs: Amazon.com: Industrial & Scientific