1/4 3/8 1/2'' Metal Socket Rack Storage Divider Rail Tray
Can't upload photo, but it's here:
https://www.ebay.co.uk/itm/1-4-3-8-1-2-Metal-Socket-Rack-Storage-Divider-Rail-Tray-Holder-150x400MM-/202184560402?hash=item2f13238f12
£8.00 from TA2 8PL
Can pack and courier at buyer cost.