There is really only one credible source for GS Mr. Color.
That would be;
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In my opinion this stuff is the best model paint in the world. I have been using it now for something like 3-4 years and it just keeps pleasing me.
I order from R10, usually with a kit or two and using EMS shipping, I usually have my order within about 4-5 DAYS! I live in the Pacific NW so the travel time from Japan might be a bit shorter than say New York, but I can't get five day service out of anybody here in the US.
And the price, even with the most expensive shipping is usually a little bit less than a bottle of Model Master at the local hobby shop. If you choose to make the transition to Mr. Color, I would also suggest the Self Leveling (??) thinner.
R10 is not as big nor as sophisticated as HLJ, but they respond to inquiries quickly and in readable English. In about five years of ordering from them, probably on an average of every couple months, I have NEVER not received everything I order from their "in stock" list.
Again, try that with any other Internet site.
Norm