A little more to implement than a couple
of switches and a couple of bulbs.

You don't need push to test, as the GPS tests them on power-up. You
don't need auto-dimming, either. A switch an a zenner will do just
fine. So, while it's nice to use the Ameri-King unit, you can roll you
own. I've flown a plane with just such a set-up, and it was IFR
approved, too.