Do you happen to have a parts list & instructions to put on of these together? I searched online and did not turn up much.I think the TekPower available on Amazon is a good solid place to start: http://www.amazon.com/Tekpower-HY-1...&redirect=true&ref_=oh_aui_detailpage_o04_s00
It is around $40 and you will need a cord from UD to complete the hookup. The reviews on this product show 90% of buyers giving it 4 or 5 stars. This unit has its own power cord and plugs directly into a wall socket. There is a large knob for adjusting the voltage and a built in volt meter. The dial is pretty touchy and the voltage display only reads out to tenths. The unit is bigger than some other choices, but if you have a particular place at home where you do most of your vaping that should not be an issue.
A couple of FC members make smaller units that use your DC wall wart as the power supply (they do not come with a plug into the wall cord). The least expensive unit sold by Voltage Keeper is $100+shipping. There can be up to a 3 month wait time for yours to be built. You can buy a TekPower and also get a portable battery pack and batteries for that same $100.
A quick word about the buck and boost units like Underdog is carrying. These are great, BUT I feel their use is limited by the fact you have to get out a tiny screwdriver to change the voltage. They are perfect for setting to a particular voltage that you have found to be your "sweet spot". They are not IMO good for stepping up the voltage during a session because instead of simply turning a knob to step up your voltage, you would have to mess with a very little screw and screwdriver. These buck and boost units are definitely worth having as they are very small and portable. Great for car use as it will keep constant voltage whether the car is running or on accessories. I put a couple of them together for around $15 in parts for each. I would not recommend some of the cheeper tattoo type units. I bought one that puts out almost as much heat as the dog itself.