Security cover for Nalgene water bottle

This thing is a security cover for a Nalgene water bottle. The cap of the bottle can open up unexpectedly in one's backpack if one is not careful. Snapping this thing onto the top of the bottle will securely hold the bottle cap and prevent if from opening accidentally.

I just used this during my trip to Sequoia and Kings Canyon National Parks and it worked fine.

After taking the bottle to Rocky Mountain National Park and leaving it in a hot car, I found that it didn't fit as tightly as it had originally. So I added some more material to prevent it from spreading. Bottletop5.scad is the updated file.

I also printed the new version in PETG which seems a bit more rubbery than PLA. Hopefully since PETG is a higher temperature material, it won't soften as much in the sun.