These are the only such cases I've found on the Internet:

http://goinggear.com/aluminum-waterproof-bunker-capsule-pill-fob-black.html
http://www.edcgear.co.uk/ProductDetails.asp?ProductCode=CC049

The first one is sold out and the second one costs $27 US to be delivered to my home. I know one of these cases is not hard to make. However, with the advent of single cell flashlights, one would think I'd have a selection of 100 different variations, each costing no more than a few bucks.

Countycomm in the US has those Delrin containers as well. BatteryJunction has battery cases but they're conventional plastic boxes, not tubes.

I have the Countycomm for both AA and CR123A batteries. They do the job.

A "keychain battery case for single AA battery"?

Don't they call that "a flashlight"?!

I found it at Countycomm.com.
http://www.countycomm.com/batterylocker.html

It's $21 with tax and shipping. I'll make my own.

That's why I alluded to the "Gerber keychain battery locker" above.

http://www.gerbergear.com/Essentials/Lights/Green-Infinity-Flashlight_22-80010

Looks pretty close to the one from CountyComm, except with more, uhm, functionality.

Yep, Gerber got a winner when they bought CMG Equipment and got the Infinity Ultra with it. It was my first regulated LED light and I have a few. Simple, and so far all are still working as designed. Using one of these as a battery case is not a bad idea, although I believe the delrin case is a tad more waterproof than an Infinity with the cap screwed out to ensure no battery drain; dunno, the Infinity is fairly tight, supposedly waterproof to a depth of 10 feet.

You could probably press one of those aluminum key fob containers into service as a battery holder for a couple bucks. Most of them are waterproof and sealed with an O-ring.

haha. I was thinking the same thing, but I'm guessing the case is meant to be waterproof?

Not sure how I like it,but interesting concept and thread.

I've thought about the extra flashlight idea. I have a Fenix LD15 and have not been able to find a smaller AA flashlight out there. The only problem is this method eliminates the guaranteed freshness of the battery. For example, someone might come around and play with that flashlight, unbeknownst to me. Or I will play around with the flashlight because, well, it's there. I suppose I could disable the flashlight, but then I might as well just use a case... decisions, decisions.

Hahaha! That's me, too. I could never have a "spare" light and expect myself not to flash people in the eyes with it!

There are some very nice inexpensive keychain flashlights out there, and in my case I use them to carry my spare AAA batteries.

An alternative is a tylenol cylinder container and duct tape for waterproofness. No keychain thingy, but you could probably make one or just put it in a pouch. Who needs all the keychain-able items anyway ; )

$13.90 including shipping, and his service is unbeatable here.

No connection. Just long-time customer who values alternative to CC.

Nice find, thanks!

Yes! I got the Delrin battery locker (and other stuff) from there already. It's on my key chain right now. It's a nice specialty item for a person who prefers a single-cell flashlight.