I believe that "cjchmical" is the ebay store of Artcraft: http://www.artcraftchemicals.com/ I have bought difficult to ship things (but not silver nitrate) from them and got good service. In Toronto there is Nymoc Chemicals. I have bought collodion, ether, nitric acid, etc. from them. They are great, but you may want to check prices, since silver nitrate prices can vary dramatically. They ship by Purolator for hazmat liquids - you have to have an account with Purolator. However, they may ship dry chemicals by other means. Also, you could pick it up at their warehouse - 24 McGee Street, Toronto, ON M4M 2K9 (416) 465-1929, (since you are in Waterloo) Murray Lindsay or John Burrows
email@example.com - tell them what you want the chemical for, and what grade, since contaminants could ruin your emulsion.