I can recommend Goal Zero products - I have many of them and I have had no problems.
One piece of advice, if you are charging your iPad directly from a solar panel, rather than from a rechargeable battery, then you need to make sure that the panel's power output is rated at least three times higher than the power requirement of the iPad. Solar panels never put out the power that they are rated at - it's usually 60-80% of their rated output.
As an example, I have a 13 watt Goal Zero panel that claims to output 7.5 watts via a direct USB connection. However it needs constant direct sunlight to come close to that. I usually daisy chain two 13 watt panels to make sure the output never drops below 7.5 watts, as this will trigger the iPad to stop charging.