ebay:
http://www.ebay.com.au/sch/i.html?_f...r2325&_sacat=0
I would try in Chinese shops.. sometimes you can find there all sorts of batteries in single package for couple of bucks...
Btw, 2325 means 23mm diameter, 2.5mm thick.
That means you could try with slightly thinner of thicker battery. The only important thing is the voltage (3V).
You can even use external supply (if desperate..)