If local sources do not get what you need, and if you do want nylon, this link gets you "close" at McMaster-Carr
http://www.mcmaster.com/#machine-screws/=5oq2ew
Click
> Machine screws
> under "material" click Plastic
> under "thread size" click M6
> choose a length, probably 50 mm
There are 8 options that cost about ten dollars for abox of 100.

I looked on the McMaster page for steel M6x50 pan head screws and the price is about the same as for nylon.

One of my instructors told me to cut an "X" in a CA hinge and slip it over the screw threads to keep the screws in the wing.