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Sirius9. DX and FT have what you want. Voltage and current can be adjusted by trimpot. They seem to work well. They look very similar to the ones in the eBay links.
Sirius9, choose one :) :
poor man's mini power supply, about for $30 :)
not a beauty, right? :)
but...
About 14-15A max current 
,of course not for so long time. The little converter is very robust.
above 100W...
The bottleneck is the laptop power supply, the protection kicks in at about 105-110W. This is enough for almost everything.
Unfortunately there is a little problem with the current regulation. If the voltage is set to a high value, and if I connect a power led to it, the initial transient can kill the led, even if the current is set to a not too high value. So before I connect a led to the power supply, I have to check and set the voltage to a desirable value, this is below 5V in case of a single xm-l.
Apart from this, it is a very useful "tiny monster" power supply. :)
Nice build viffer 750. Very creative.