Holley fuel bowl thread tap

Hello guys

I'm repairing a holley carb at the moment and one of the long fuel bowl bolts has broken off. Can someone tell me which thread tap I need to get a new bolt in? I allready got a UNC 1/4 tap bit thats to big. Here in Holland we only measure in metric. So bit of a hassle to find correct thread tap.

Thanks guys.

Gr Arnoud