Dirt cheap solution
If you aren't worried about quality,
try my $20 trick:
Buy a pair of ear buds, the kind without any sort of strap, or any too large bit of plastic sticking out (you'll see why in a sec).
Then buy a pair of those industrial hearing protector earmuff things from Home Depot and cover the ear buds with them.
If the ear buds are too large then the
earmuffs won't comfortably cover them up..
The isolation is quite good, the ear protectors work in both directions.
You're sound quality is limited by how good a pair of ear buds you can find..
Gord Wait