For Canadian like me who owns a Boxster with an American MPH cluster, there is a solution...
I found that FVD Brombacher is selling metric Gemballa gauge face at clearance price.
I've purchase a full metric set in KMH for $120... lot cheaper than a new cluster...
And for American they also have MPH gauge face in many color.
Here is the link to FVD Brombacher
FVD Brombacher Gauge face