On 20 Aug 2020 21:55:33 +0100 (BST), Theo
wrote:

jkn wrote:
Hi all
you know those flat metal 'Tradesman's' cases you get of screws etc -
with several plastic 'sub-trays' of different colours and interlocking
sizes. for the different sized fasteners?

Any idea where I could get sets of (cheap) replacement sub-trays? I have
only found them costing several pounds per tray, even on eBay. There must
be someone who sells a knock-off variant. I have a couple of empty cases
I want to fill...

No idea if it's the sort of thing you mean, but:
https://www.aliexpress.com/item/4000148629309.html
https://www.aliexpress.com/item/32998017798.html

and similar sets of interlocking parts.

Don't expect to be thanked unless they are *exactly* what he's looking
for ... and those wouldn't let him throw his toys out the pram fast
enough. ;-)

Cheers, T i m