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....................Pinholes the size of yours can be drilled with a no. 74 or 75 drill, perhaps obtainable at a hobby or model shop. ..........

I assume that the whole world is in inches.

A # 74 drill is .0225" [.571mm] in dia
A # 75 drill is .0210" [.5334mm] in dia

Here is a link to a drill chart.

http://www.carbidedepot.com/formulas-drillsize.htm

I hope that at least the drill chart helps.