A year ago, I found a recommendation for, and bought batteries from www.bestbatt.com (US) for my Panasonic camera.
A single spare battery (in AUS) from Panasonic was about $80-100 which is a bit rich, so I ended up buying 4 batteries from Bestbatt for $52 shipped to Australia. So far they have performed perfectly, and I never get caught out with a flat battery.
Be aware, I have read that some software may check for the presence of OEM battery only before operating.
There are many other places to buy from, and I can only suggest the one I have used, where the range of batteries is staggering and the online service was excellent.
Jim