You need to work on your google foo

2 seconds of ebay searching for "3/8 bsp hex"

https://www.ebay.co.uk/itm/1-8-1-4-3...cnQ:rk:18:pf:0

https://www.ebay.co.uk/itm/3-8-BSP-H...Wdg:rk:32:pf:0

https://www.ebay.co.uk/itm/Set-of-5-...Px0:rk:45:pf:0