The Seagate Game Drive External SSD is available to buy now, and it works on both PS5 and PS4.
https://www.techradar.com/gaming/seagate-launches-all-new-external-ssds-for-ps5-and-ps4
https://www.techradar.com/gaming/seagate-launches-all-new-external-ssds-for-ps5-and-ps4