I was in the US a couple of months ago and got them from diycable-Kevin Haskins used to assemble these units but stopped doing so a few months ago-however he has some parts that go into the build, details of which which are available on his site, I suggest you check it out and if you have any specific questions, just ask.
In addition he was good enough to use his connections with Hypex to order them at a good price. Essentially he offered a custom power supply board with capacitors and a mounting plate, as well as a softstart module, in addition to the Hypex modules and cables. The price is about $750-800 IIRC, excluding the toroidal transformer, input and output connectors and misc hardware, and chassis. It might add up to just over $1000 give or take.