Ther was a solar / USB 2x AA charger from Kodak - also appeared under some other names, cheaper - the solar charge is VERY slow (needs 28h for full), and it cannot charge & run at the same time (guess the same power converter is used for regulating the charging or the 5v output).
I have one, in the form of the "USB5000" - not sure if they can still be found
http://www.amazon.com/T-5000-Hybrid-.../dp/B003EW82ZG
Not sure if they ship to NZ, but if you want interchangeable AA cell device instead of a built-in LI-Ion, not sure how many other options there are.