As far as I know they are completely unavailable in the USA. I don't think anyone online is going to have them unless you convince someone in Europe to ship them over here, and I don't think they can do that.
What I heard was, and it could be wrong, that Tamiya doesn't adhere to the US requirements for labeling (basically, "Don't Drink This Or You Will Get Sick!") so they can't sell them over here.