Google has indexed thousands of publicly accessible HP printers
Idea for startup.1. write a script to scrap google links to HP admin panel2. filter out the IPs that are from US (given you want to work on US market)3. assemble the list of printer types and current toner levels.4. write a script that will print to each of those printers a one single page, stating your company "Cheapo Suppliers Inc" was notified that "your printer is low on toner. Call xxxxxx to re-fill. Lowest prices quaranteed within one day delivery!". You can add link to your shop page that already redirects user to specific type of printer they have, some type of one-click order (based on which toners are low).5. daily rinse repeat.6. sell your business to HP (at least try to).