OP, either order directly from Mayhems or go through Aquatuning.
I can reccomend Aquatuning based on my experience with them so far. True they are based in Germany, but they offer a 2 or 3 day shipping option with UPS, they take care of import fees and they usually dispatch same day (keep in mind they are a few hours ahead of us).
The only dowside is that the shipping is a little expensive unless you order over $75. They charge $8 / $6 for 2 / 3 day shipping respectively, plus $10 "small order fee" (orders under $75).
I'm sure Mayhems are just as good shipping wise, I have not heard anything to the contrary, and if you are just after a few bottles of the dye it is probably cheapest to go straight through them.
Oh Mick, glad to see you are stocking the DT 5Noz - way to support the WC'ing comunity