The RTX 3090 can be bought online from any major retailer or Nvidia's official website if you want the Founder's edition. However, Amazon is the most prominent market supplier, offers the best rates and the best after-sales service that you can access via the provided links in each recommendation. Gigabyte GeForce RTX 3090 GAMING OC is the fastest 3090 with boosted clock and offers the most extended warranty of 4-years among all 3rd party RTX 3090s.