BlitzWolf® 15W 2A Foldable Portable Dual USB SunPower Solar Cell Panel Charger with Power3S using coupon code D321CD brings price down from $32.99 to $26.39 (20% or $6.60 less). This panel can easily charge any smartphone and will also charge in overcast conditions as well (with decreased rate of course).
Registered shipping included but currently in preorder - stock is due to arrive on May 31.