For wireless microphones, and really anything that requires serious staying power from 9v battery, let ProCell be your first choice.
Broadcasters, Stage Managers and Theatres all around the world depend on the battery that gives them maximum output for as long (and consistently) as possible.
Grab them by the carton (12 per carton) - heaps cheaper than your local supermarket. Also get a box for your kid's toys, remote controls and other gadgets...
- 12 per carton
- The price listed is 'per battery', not carton pricing