I have actually used superglue (cyanoacrylate) for this without ill effects. It's not solvent-based and doesn't dissolve rubber (even natural rubber, which this probably isn't). The downside is it's brittle, but for feet that's OK unless you make a habit of dragging the case around. Some "rubber" materials don't bond well, but adhesive companies recommend trying cyanoacrylate first. That link is worth a reda as it mentions degreasing the surface first, and a few other tips. Superglue should also stick to the paint fairly well, though a bit of roughening may be in order.
2-part epoxies again aren't solvent-based and won't attack the rubber, but they don't bond to it as well as superglue, and the rubber easily peels off.