I highly recommend this source, Megachef Oyster Sauce (Gluten Free) - The Mala Market
Its a wonderful site run by a woman in Tennessee who adopted a Chinese orphan years ago. Not wanting her daughter to lose her cultural heritage she became obsessed with Sichaun cuisine. I have ordered from her many times, and the quality is far better than anything I have found here. There are wonderful recipes on her site as well.
Food and Wine wrote her up in their last issue.
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