Hey Mate,
I can put together a scraper for you that will scrape all sites every x minutes and store the data in a db for further reference. Any new entries will trigger the discord API and whatever channels you have tied to the app. I just need to know how you want the 'add to cart' bot to work, do you mean you want a bot that links to the site for you or a bot that automatically purchases for you?
Cheers,
Elliott