Wallet Cache for Hearing Aid Batteries

Modern hearing aids are a true marvel of compact electronics and I find it surprising how long they function on the miniature zinc-air batteries. Not surprising, the batteries seem to have a "habit" of dying when I'm away from home, as often as not. That is why I made this "Wallet Cache" at the Techshop, San Jose,CA, www.teschshop.ws.
I used .090" acrylic form a local Home Depot window department and laser cut the holes to be a light press fit for my batteries. There's no magic to having six holes, it just seemed like a good number. The outline dimensions of the acrylic are the same as a credit card. 
I engraved the battery type on the cache, just for good measure.
Now, as long as I keep the  "Wallet Cache" replenished, I have fresh batteries at hand wherever I go.