From the Ruff Cycles home page, click on Buy Ruff on the left.This will bring you to a map of dealers and contact info.The price will vary by location due to high shipping costs.
I'm building one now, the site above has them or if you want to save money, but wait, buy them from Germany. Took 3 weeks for mine to arrive, but I saved 150 bucks, not including shipping so around 175.
There are a few US dealers I would recommend you support. You may pay a little more but its supporting those shops that the hobby grows. Those shops make big investments in facility and stock. They are also typically the people that have the cool parts from overseas.
Nick at local Cycles or Dom at The Cruiser Shop both of those guys should be able to help
If Ruff is selling frames direct to consumers in the US, I would be pretty upset if I was one of their Dealers.