You might try to find a local gunsmith and see where he gets his
taps and dies locally. I know you are out of the states. I prefer
the gunsmith grade taps and dies.
Of course in the states,mcmaster or msc would have some. they
usually have a G3 number or something similar marked on them.
I would also use something like rapid tap or something with paraffin
in it. I work on lot of dies and stuff and usually prefer a quality
tap. You also need to consider getting the appropriate drills that
you use to make the pilot hole and whether you need a bottoming tap
or not given if it is a hole that goes thru the metal of if you only
going half way. You could download a chart telling you which taps to
use whether coarse or fine and the appropriate drill size for this.
Have a good one!
Indian Jewelers Supply Co.