The most common decoppering agent used in powder is tin dioxide. Although lead and bismuth compounds can also be used I don't think anyone is using lead because of the environmental and health hazards.
You can add IMR-4166, 4451, and 7977 to the list of powders with copper eliminators in the mix.
I know that the new M855A1 round requires copper eliminators in the mix, but I haven't seen any of that surplussed out yet.
Jimro