The best bang for the size is universal fit in-ear monitors from someone like Westone, Ultimate Ears, Shure, and many many others. You'll get great sound reduction, since they are essentially ear plugs. If you have the funds and don't mind things in your ears then you can go with custom in-ear monitors. These will reduce outside noise better than sound canceling headphones but many people don't like in-ears.
Sadly Bose makes probably the best noise canceling over the ear headphones. They are spendy though.
You might get better results searching the forums over at head-fi.org
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