batteries...................
www.duracell.co.uk does procells for about a quid each...spend a couple of quid on decent non rechargeable batteries for a tournament and make sure there is a fresh set in first thing in the morning.
tescos do a four pack of duracell 9v for just over 8 quid. when you are spending lots of money on paint and markers, don't forget your little batteries!!
failing that buy some QUALITY rechargeables and use them at training etc.