The book doesn't deal with this case specifically, so it's up to the DM.
If the armor is nonmagical, it's pretty clear that you can't use something designed for normal humanoids. That's just from common sense, because regular armor doesn't have big holes exposing the shoulder blades. In a city of non-winged humanoids, you'd probably need to get your armor custom-made.
With magical armor there's more room for argument, since magic armor normally resizes-- the same suit will fit either a halfling or an ogre. Some DMs extend that to the point where armor will automatically reshape as well, to accomodate wings, tails, or other extra appendages. I don't happen to like that idea, but again it's up to your DM to decide.
IMC, I would consider you a "nonhumanoid" creature in terms of armor, and charge you double the base price (not counting any masterwork component or magic enhancements). If you found regular armor and wanted it modified, I'd have an armorsmith charge you the armor base price, so its value would come out the same as if you'd bought custom armor and then enchanted it. That is, modifying that suit of full plate would cost you 1500 gp.