According to here, it maps to Speed Bleeder 1010S
101 Projects for Your Porsche Boxster: Project 48: Bleeding Brakes Parts
Which is M10x1.0 with a length of 31.35 MM
Speed Bleeder Sizes
I'm about to have to do this as well as one of mine is weeping even after it is tightened down all the way. Let us know what you get and how it works out.
Steve