Two days ago I found this nice piece of hardware on Ebay.
Out of that I build a solution how to power-up the lnb for a portable setup using a notebook with battery only.
You see the bias-t connected to the 5V-usb to 12V cable, the F-cable from the bias-t using a F to SMA adapter to connect this to the rtl dongle.
With this setup it is very easy doing portable operation on QO-100 without the need of an additional power supply..