These a 10W panels for $50. Not yet in stock in the US, they had to special order them from Hong Kong in January, just arrived today to my home in Austin on March 20.
I will be reporting on how it goes.
 17:40 update
one more hour, this time I had set the panel at an ideal angle. 82% charge after boot. That is, 30% increase in the last hour, that's more like what we had in May. OTOH, we're getting closer to sunset, so performance will likely go down now, I might not get 100% today even if I massage the panel position. But 100% charge seems possible in 3 peak hours.
 16:40 update
I have had an XO charging for 3:30 h now, from flat - no response state. Not an ideal angle for the panel, but nevertheless I expected more than 52% battery. Same placement than the May 28 test, so, yes, the sun is lower in the horizon in March.
 Just arrived
- Notice the XO Charger is rated at 1.42 A (that's 1.420 mA)...