Considering most characters under 5th level don’t have a detectable alignment you would be better off not detecting a specific alignment at low levels. If you have Champions of Corruption the feat Mask of Virtue sounds like it would make it so that your alignment is not detectable.
My character is an Aasimar, an Outsider, which means I get an aura at level 2. As far as mask of virtue is concerned, My DM is higly likely to make me roleplay the fiendish pact for mask of virtue ingame after I find a demon to pact with. I doubt that would happen at early levels.
Angel hide or angelskin armor can mask your evil aura. It's about +1,000 gp for light armor.
Ditto the Angel skin. I'd have to find it ingame. He's a stickler for rare things to be found ingame and roleplay their discovery. We've had to quest to find adamantine and mithral in previous campaigns because "why the hell would a human smith in a town like this who fixes plows for a living have a store of mithral large enough for full plate just on-hand whenever? No, there's a dragon in the old castle/dwarven settlement under the northern mountain range/bigger market in the capitol to the east, go find some g*@#&~n mithral and bring it back."That's the trend thus far anyway.