Help me find this herbal product

I’m looking for guaicum*, the natural product that the expectorant guaifenesin is a synthetic of. It’s apparently a gum or resin from the bark of a certain tree. I’ve found herbal mixtures with it as an ingredient, but not the pure stuff. I’ve also found a zillion sites for the wood of that tree (lignum vitae), but not the herb. Ideally I’d like to obtain it as a tincture.

  • = guaiacum, guajacum, guaicum officinale, gum guaicum, guaiac resin, gauiacolate, chobehyat and possibly more.

It’s clearly not for sale on the Internet, with only 70 results total (and I went through them all). I would suggest hiring a Google Answers researcher to do some offline research.