I'm using a old LCD monitor power supply as a DC-Dc.
It' s a 12V 4A switching that normally take 100-240Vac but i discovered two years ago that some of them acept DC current at input !! some can take from as low as 20Vdc only!!
so that make you a cheap dc-dc that can take any voltage from 20 to 240V ac or dc !!
you can also buy some from ebay at 9.99$ that are rated 12V 4.5 A. they generally all work!
if one dont work.. you can try reversing the polarity at the AC input.. sometime it only can take one polarity cause it's dc and not AC at input.
sumarry: many simple AC switching power supply adaptor can work as Dc-Dc !!
since these Ev200 can take between 9 to 36V DC input you can use ant of these adaptor that have between 12 to 24VDC.. they will work.
I know that many laptop psu that have like 18 to 20Vdc output generally work fine for that too.
You only need to ensure that the inruswh current when the contactor energize can be supplyed correctly. and that the psu have at least 4 or 5A output for that. You can also add a capactitor in parallel at the output to help for the inrush current of the contactors.
My actual mongoose work fine with a 4A 12V external psu from LCD monitor connected with 50 or 100Vdc on my konions.
I hope that help!