Hi,
The manufacturer will tell you about the horror stories of a leaking battery wrecking your camera and they would be correct. However, I have bought a few aftermarket types for a few of my cameras and they have been fine. I would admit that one of them died after a couple of years of little use but this can happen to any battery. My only recommendation is that you don't leave a battery in an unused camera for any length of time as this will increase the risk of leakage. I use the camera and then take the battery out before tucking it away. I think I bought a pack of two for my canon camera and they cost me about £10 or so. Good value as far as I am concerned.