Like has been said, most commercial chili powders are mostly ancho. Depending on the recipe, I wouldn't worry too much about finding pure ancho. I've got straight ancho from a local spice store and can't tell much difference from a McCormick's dark chili powder.
Pork Pullin Plowboys
(and Smoke on Wheels
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Todd Johns (me); Blue Springs, MO
Randy Hinck (PigBoy); Concordia, MO
Andy Groneman (Hodedo); KC, KS (Cameo Appearances)
FEC-500SS; FEC-100 (Right handed); FEC-100 (Left handed); Country Smoker Tailgater; Big Green Egg (2-large, small, mini); Cookshack Pellet Fired Charbroiler