Yves;
Hi!
I've had some good experiences with "Sharpie" "Ultra Fine" "CD / DVD Markers" - the type with a tiny and skinny fibre "pen nib". I use them for some chipping and also for drawing in fine "paint lines" on things like French WWII camo schemes where colours were demarked with black boundaries.
There may be two (2) different "blacks" available from the different Sharpie lines.... those labelled "CD / DVD Marker" appear to be a red-black, whereas those labelled "Sharpie Pen" seem to be a green-black (there are no black-black types.... ink chemistry limits, I guess).
Both: Permanent ink, capable of reasonably dense and opaque black, and you can reliably get a nice line down to around 0.2mm wide. I have altered these to go smaller by carefully slicing off at a diagonal the tip with a very new Exacto blade or razor blade. This yields more of a "chisel" tip and can make for finer lines.
"Sharpie" markers and pens are widely available across the USA - Not sure but suspect they are readily available up in your neck, too.
I've attached a pic of my Renault R-35 build WIP to show these markers "on the job".
Bob