I've seen concentrations of 2%, and would not expect much more from OTC sources.
Got democracy? http://www.dhushara.com/book/multinet/democ/wed.htm (http://www.dhushara.com/book/multinet/democ/wed.htm)
The packs i have seen, are about 100 g.
The cost is reasonable if one were to process a small amount.
EDIT: sorry hidden cloud :-[ . Your powders look better!
Got democracy? http://www.dhushara.com/book/multinet/democ/wed.htm (http://www.dhushara.com/book/multinet/democ/wed.htm)