Google shopping (which can lead to hundreds of vendors), Fleabay, Amazon. I will also google the tool number to see if it turns up at other vendors, not listed in "google shopping" Google is goofy about the way info has to be fed to them, for your "stores" inventory to make the google shopping list.
I find some of my best deals, buy working the numbers, not the vendors.
Most my purchases come off ebay, then Amazon, and the various sites, including GJ, and other forums I frequent. I even buy stuff from wally world online, the HD, because their shipping is so cheap, I cant drive there and buy it, so I have it shipped.