Just as a word of warning - I bought a 2200mAh battery for my H320 on Ebay, it was listed as a generic 1st/2nd Gen Ipod battery.
The battery is absolutely fine but is just slightly too big for the H320 - I've had to remove the blue rubber protective padding in order to make it fit - and even then it's still very tight in there. For my purposes, losing this padding isn't too much of a problem (I think) but other people might be using their recorders in situations that would make that protection crucial...
I'm told that the small capacity batteries do fit better, so it might be somehting else to bear in mind when making your choice.