Where can I get stump remover in Norfolk,On?

Where can I buy stump remover,salt peter,or potassium nitrate(kno3) in norfolk county or near there. I've researched and the closest one i've been able to find is Plant Product in Brampton . Pharmacy stores I guess need a liscence to sell it now so most don't sell it. You'd really help me out if there is one. Thanks