Or...whatever you call those things that aren't quite backgrounds, like Bottled Hatred (perfect, but out of my budget) and the like.

I'm looking for one that's cheap and doesn't look like it was drawn in five minutes on an off day (tried a couple that looked a lot better on the model than my actual HA...).

Not sure which items you've already tried, but these are the ones that come to my mind: and its two other colors (Mysterious and Spooky) and other colors

These are kind of pricey but have similar effects to Bottled Hatred:

I think covered most of the cheap auras but here are some budget backgrounds for you. I hope this helps.