Is there a place to sorce simple 3D animations I can bring into Adobe Aero?

adobe's mixamo has a bunch of animated 3D animated characters

Sketchfab has a bunch

pre-animated assets are a bit more of a challenge given animations are typically unique to each situation.

You could check CG Trader and Turbosquid.  YOu can certainly find pre-rigged assets there - some may also be preanimated.  You can also check Adobe's Maximo product.  They have pre-rigged and animated assets - however, most are humanoid.