I have small foldable solar panel that weighs 12 oz, measures 9"x6" and it puts out 10W in direct sunlight. It will charge an i-phone in 60 minutes. I have not used it on my bike because my Panasonic 3400mAH batteries provide plenty of power for an allnight ride and carrying a spare set is much easier and lighter than trying to charge on the fly.
This is the panel and battery.....Instapark® Mercury 10M Solar Panel Portable Solar Charger with Built-in Dual USB Ports for iPhone, iPad & all other USB Compatible Devices, 5200mAh Battery Pack
I understand what you mean. I guess i really dont need anything. I am sort of experimenting with ideas more than anything. I wish i could put a solar panel on my apartment but apparently too many trees and well no chance of me having that sort of money anytime soon. I will dream on it though he he...maybe i will get a foldable thing like yours in the future :0)