If you want just the grip consider the CTA grips http://www.amazon.com/CTA-Digital-Vita-Hand-Grip-playstation/dp/B0073ESZ58

I was tempted to get the nyko during the sale last week but decided to just get the CTA instead as I had read about the battery dying and didn't really want a battery to begin with. The CTA seems to be the same design with the same locking mechanism, but it uses pure friction instead of the charging port. Cheaper and (I assume) lighter as well.