I needed more storage on the Battery Holder by jgillick so I decided to increase the height but didn't want to reprint base and waste filament. So I built some height extensions.
You should find STL's for a single height extension and a double height extension.
The STL's are sized for AA batterys, if you want to rescale for AAA then change the scale to for X to 0.89 or 89% and Y and Z to 0.73 or 73%.
Hope this helps someone.
I've just noticed that kelticsylk also designed a similar item Battery Hopper AAA Extension, I didn't even search for this before creating is great minds think alike!