Andy Burns wrote:

M5 x 12mm countersunk, pozi, black?

You probably don't want 1,000

https://shop4fasteners.co.uk/catalog/product/view/id/102572/s/pozi-csk-flat-head-machine-screws-steel-black-finish-m5-x-12mm/category/4034/

might find them easier if torx or allen-key heads are acceptable?