I've been very happy with the Logitech solar keyboard for mac. Feels good enough, and you can't beat that it never runs out of juice if you're in a room with a window. https://secure.logitech.com/en-us/product/wireless-solar-key...
Extra: the numeric keypad is a great addition for me personally, as I do/learn Blender modeling in my free time where having the numeric keypad is really required.