The nuts for the stainless might be Zagato specific, but there is hope.
you can buy a similar nut in Stainless steel, galvanised or yellow cupper
The DIN number is 466 and than you get a nut that looks like this
Kartelmoer M4 RVS.pdf
I can order them down the street at our local Fabory shop.
Stainless will cost me 2,75 Euro each, excl VAT with a minimum of 25.
Galvanized ones 0,63 Euro each, excl VAT with a minimum of 50.
This is for M4 nuts. Delivery time app. 3 days.
I'm thinking of ordering a box of galvanized ones, but than I'm stuck with 46 nuts which I'll never use again.
Don