Just found this system for sale in the UK, it comes with 4 wireless sensors, 4 alloy valves, the main unit and power adaptor.
Tyresure 4 Wheel Car and Small Van - £179.00 : Ecotune Sussex, fuel saving, wheels and tyres
They say to contact them if delivery is to be outside of the UK.
Just thought it might be of use to somebody, Measures up to 60PSI too..