You can use any USB HDD casing. A fan isn't usually necessary as long as the case has reasonable ventilation. Performance is not an issue if using for media so I'd go for something low cost.
2.5": https://www.amazon.co.uk/ORICO-Enclosure-External-Tool-free-25PW1-C3-Black/dp/B0B92C5DSB/
3.5" and powered (large 3.5" HDDs have high power draw so a powered caddy is best): https://www.amazon.co.uk/RSHTECH-Enclosure-External-Automatic-Function-Sliver/dp/B087WQN725/