I thought I'd see all the _____fire batteries but the FANDYFIRE takes the cake! Some of the local stores will sell the plastic boxes and some give 'em away. Depends on the store.
Anyway, I like the plastic ones to carry the spares in my pocket.
Electrical tape gets messy with in no time with just body heat and will leave a sticky residue in your pocket.
And, for the sake of mentioning, policemen used to carry spare batteries in their pockets with bullets, and yes, occasionally a bullet would go off in the pocket. I can only imagine an officer explaining to his wife why they'd never have children of their own.