Poster Purchase Bot Needed

I need a bot that will monitor & auto-purchase posters from the following site: mondotees [.com] Please visit the site and select one of the in-stock posters to see how the purchase system works—it's quite simple. Also, the site recently changed to use Shopify. The way the site works: - Posters are released at random. The bot should be monitoring this and select the poster I specify (I only want certain ones, not all). - As soon as the poster becomes available it needs to add it to the cart. From the Cart page select "Checkout with PayPal" and sign into PayPal to process payment. - OPTIONAL: If possible, I would sometimes like two different posters to be added to cart (rather than just one) before proceeding to payment. There are no captchas or safeguard preventing bots on this site. This needs to work very fast. Posters can sometimes sell out in under 30 seconds. It's not uncommon for the site to become overloaded with traffic and become non-responsive if you don't purchase the poster very quickly. Thank you!