I do live in the states in South Carolina, the original peltier link did not work, but this one does and that peltier is fine and a good price too.
As to whether the motor voltage controller will work? IDK
I control the cold output with the TRUEs cooling fan, I do not allow my computer to stay on all the time, only when I use it, so it's only drawing power to run the peltier or peltiers when it's running, so I do not need the voltage controller.
For your information gathering, my reservoir is not insulated to the point of long term cold retention, it's insulated for short term cold retention, meaning after it's been turned off for 12 hours the water temperature inside the reservoir is still below, but very close to ambient.
The reason for this is it avoids any cold booting problems and once the machine is powered the water temperature begins to drop, and continues to drop until it reaches and equalization point usually 7c ~ 8c below ambient room temperature.
A traditional radiator loop starts at ambient and increases heat in the above ambient zone until it reaches an equalization point above ambient, whereas mine starts close to the same but goes in the opposite direction to below ambient.
In the beginning I did play with controlling the voltage, but it caused the peltier to stall, getting what you can use from the peltier constantly, will require a constant voltage, at least in the way I am using the peltiers output, keeping it in a range of constant cold output.
I know some of this doesn't make any logical sense, the peltier is what it is, and sometimes reacts peculiarly, but you can milk what you want from it and enjoy the benefits, as long as you discover how to get what you want from it, without it stalling.
Once I discovered it's cold output could be controlled with the cooling fan on the Thermalright TRUE, there was no further reason to experiment with voltage regulation, so if you are going that route, please share what you discover.