Nikon En-EL4a Battery

I'm looking at where to get best deal for a EN-EL4a battery. They are all very expensive on the local dealers I've seen. 
Do anyone here uses a third-party EN-EL4 replacement? Any idea how that would perform to the genuine one?
Where would you guys suggest to get one of this?

Do anyone here uses a third-party EN-EL4 replacement? Any idea how that would perform to the genuine one?
Where would you guys suggest to get one of this?