I agree, 4227 is much too slow a powder for use in a low pressure cartridge like the 45 Auto. Using it in the .44 Magnum is a very good idea.
Luckily there are MANY powders that will work well in the 45 Auto, actually well over a dozen powder. Even now you can probably find one or two although very sparsely!
Clays, Titegroup, HP-38, Universal, 700X, PB, SR 7625, SR 4756, Trail Boss, W231, AutoComp, WST, AA#2, AA#5, ZIP, Bullseye, Unique, Promo, Red Dot, Green Dot and some VV powders and probably a few more I didn't think of.