Steve G0XAR brought up a "Wind Generator", which could be useful for powering an MEPT. Guess what, I could not resist and bought one.
This is what I got for just £9.95:
What you see is, the wind generator, a USB-cable and a set of adapters to connect a device to be charged. Interestingly there is a 5V PSU supplied, which, at first sight seems not to make any sense.
However, the device is called "portable power bank" and actually carries an internal 1200mAh accumulator. Meaning it is supposed to be carried about for charging up other gadgets with 5V supply voltage. As preparation for outdoor activity, the internal accumulator could therefore be charged from mains supply.
Surprisingly, the optional bike mounting bracket was included in the package! Many thanks to "ecohamster"!
Very unfortunately, the device is not weather proof. The manual reads that the wind generator must not be used under wet conditions. That is, I believe, a huger downer!