I got a handful of externally ballasted 26W mushroom fixtures from Home Depot a few years ago.  These used a g24q-3 socket to accommodate 4-pin quad lamp like PL-C, Dulux and the like. 

They don't have these anymore.  The new one is a dreadful GU-24 socket type.  No ballast in the fixture, but comes with GU-24 socket CFLs.  They're exactly the same as normal screw-in CFLs.  Integral ballast.  The sole purpose is to prevent the use of normal incandescent lamp in the fixture to satisfy title 24 energy code in State of California. 

I'm not in California, so not only do I have crappy built-in ballast CFLs, selection for replacement lamps are limited and they're expensive.