Try here! Plenty good enough for one show, and with "kind" mics, more than one. That said, the comment about the newer mics running on a pair of AAs is true. Again, good for at least one show, and even if you don't want to risk two, they will do a rehearsal as well.
Duracell Procell Battery Alkaline 9V Ref MN1604 [Pack 10]: Amazon.co.uk: Health & Beauty much better than the GP.
If you can find them cheaper from anyone other than Amazon, please do. I don't like giving the tax dodgers my money.
Why not use rechargeable batteries? We use them with our Sennheiser mic's very successfully - Duracell 2400mAh ones. A pair will last ages. Then you slap em in the 1 hour charger and you're ready to go again.
Many pro's don't like rechargables for three reasons:-
1) They start out at a lower voltage.
2) If doing a big show, with many sets of cells, it is very difficult to be sure you don't mix up part charged and fully charged cells.
3) The discharge curve is different to an alkaline. The mics sensing circuit will be off, and the battery "dies" suddenly rather than gracefully.
As to using Pro Cells, well all I can say is advertising works, doesn't it? The GP batteries are fine, and a whole lot cheaper. I've used hundreds and never had a dud one, I can't say that for Duracel. Some mics will be intermittent with Duracel as the positive "pip" is less pronounces, leading to poor contact.
We work in schools, not the West End. A pair of charged rechargeable batteries works fine in a school. Even for 2 hour long shows. Managing them is easy One box for charged, one for empty. If you're really uneasy, swap at interval.
Buying single use batteries is simply wasteful in a school.
I would never ever use rechargeable in my wireless mics, infact I think the manual says you must not use them as well.
I have only ever use Procell for shows and events that matter, rehearsals, school disco etc... we do use the cheap greencells if it dies its 2 minutes to slap some more in and you don't have embarrassment in-front of parents, potential parents, paying guests etc... as you would with major events.
Batterys are used for one show only then kept for extra rehearsals, remotes, LAN testers, Clock Batteries etc.... its just not worth the risk if you know where to shop decent batteries don't cost the world.
I've been using rechargeable batteries with Sennheiser radio mics since I was 14. Never once had an issue, but have saved my various employers thousands of pounds by using them, and haven't been ruining the environment by using single use ones either.