Hi, I actually built my own solar panels as it was both cheap and easy to do... Everything I got from ebay...
2 x solar cells 7.5v @ 500mah
1 x voltage regulator 5v @ 500mah
some usb connectors
From here you can wire the panels up in serial or parallel to get either 15v @ 500mah or 7.5v @ 1000mah, you can verify this with a multimeter... The voltage regulator then regulates the voltage at 5v 500mah to make sure it never lets out more power than that, so you wont kill your dingoo... Then a female usb connector so you can hook up a usb cable to your dingoo...
It's almost as easy as hooking up a light bulb to a battery... you can find guides on youtube and google.
I would link you to the items but there of course not there now due to the items being sold on ebay...
If you want to take this route then please feel free to get in touch and ask questions...
Oh and from this setup I've managed to charge up two of dingoo's a few times and play some gigs using piggy tracker