I started a somewhat similar thread a few days ago, and got recommendations for a couple of good suppliers, one of them was:
http://www.digital-speedos.co.uk/
where I found these gauges:
http://daytona-global.com/products/?page=Products_AllProducts&mfrID=9&categID=14&subcategID=49
Japanese made, matching electronic speedometer and electronic tachometer. And reasonably priced too. MPH or KPH does not matter, as it all depends on the wheel circumference entered into the unit. If the unit is "metric", then just enter circumference in mm diveded by 1.609.
The tachos are either 8 or 18000 rpm, which is a bit of a shame. 9 or 10000 rpm would be perfect for the XS, but I believe I will go for the 8000 rpm version. Right now I am waiting for a reply from digitalspeedos.co.uk on a few questions on these Daytonas vs some alternative gauges from KOSO, that has 9000 rpm tacho, but look a bit too modern to me.
I have a KOSO RX2N electronic tacho/ speedo/universal instrument on my Monster, and it has worked great for the 3 years I have had it. Actually, BIMOTA of Italy used a KOSO RX2N on one of their later DB models, with a customised gauge face with Bimota logo.
Before the KOSO, I had a Autometer-Procycle 5" Monstertach on the Monster (!) but that unit died after a year and a half.....So I have no reason to doubt the quality of KOSO gauges, at least compared to other brands on the market.