ProtegeManiac
Headphoneus Supremus
Folding isn't a requirement if they come with a headphone case then that's fine, I've purchased a bag big enough to hold headphones that don't fold, the seal around the ears isn't a problem either as the leakage from there isn't massive and not noticeable I think, I'm not going to be one of those annoying little pricks sat on a bus with death music at max volume., I like my ear drums.
Read up on the Beyerdynamic T70P, and the T5P if that one still fits within your budget, see if the feedback so far sounds like what you want.