While I think the best way to carry 123-size batteries & a SureFire lamp is to use the SF Spares Carrier, it is bulky.

I've found that a Kodak Advantix film cannister (oval shaped) will hold 2x123 batteries just fine. Add a piece of gaffer's or duct tape to keep the lid on, & you're good to go. BTW, the Fuji cases won't work...they're slightly smaller than the Kodak.

You can pick up the cases at practically any photo processing shop, free.

David