Thanks for your response and suggestions. The screw is from a slide that runs along a aluminium track. The slide is attached to a safety cover for a swimming pool (Aquamatic swimming pool cover). These slides with screws are £65 a pair and changed out a least twice a year, so was thinking of making some.
if you are making from scratch do they need to be those exact screws ? couldn't you just substitute for some other ss screws that would be fine in plastic / nylon