jake mentioned a company on some thread somewhere, STF or here (REALLY need to find that because i am having a hard time finding the same info on the web), called Westech. They make aircraft gauges to your specs. they have a circular or square gauge they can build with all four CHT's in one gauge. pretty sweet. that is NOT the low cost solution though.
but not real expensive as i recall.
someone let me know if you find the site page with the gauge build info.