20 4BA x 7/8 Countersunk (Flat) Head Slotted Screws Plated Steel | eBay
Found this on EBay.co.uk
I know that I is not what you looking for.
But I have a similar problem two years ago
First put them in salt assid too remove Zink
Put them in drill an with a fine file form the head as you like.
Shorten them.
You can now soft solder them an blue them.
That was what I have done. It looks ok I think at least.
I am on hollyday but can send pictures when I am home if you want
jsne
I am not sure if the link works
It is all done by my phone