Just got my new JCWhitney Truck catalog, and they have "generic" A-pillar gauge pods for 2 1/16" gauges, in single, double, and triple models. The ad says to use a heat gun to form the pod to your pillar (makes sense...). I think the triple was $30, single and double a little cheaper.
They're probably not the prettiest pods out there, but they'll do the job. I'd get one if I was running the small gauges, but since I've started a collection of Autometer Sport-Comp 2 5/16" gauges (or whatever the bigger ones are...), it won't work for me.