Omori makes 45mm gauges, but I'm not sure if those would fit. They used to have 42mm gauges back when I had a SW20. I think they also make custom OEM gauges if you want.

Here is a link to their website (45mm Boost Gauge):
http://www.omorimeter.com/45mm_multi...ost_gauges.htm

Gruppe-S sells omori gauges for the WRX, but they are 60mm gauges.

Although RallySport Direct has the 45mm Versions, but only the boost gauge: http://www.rallysportdirect.com/shop...0_249_667.html