Buying shoes online

Can anyone recommend a place to buy larger than usual footwear? I'm looking for shoes for my teenage son who takes a size 12. He likes Vans, and places like High and Mighty have very limited stocks of this sort of stuff. They are also very expensive. I found a couple of places in the US (Zappos.com for example) but they don't appear to ship to the UK.

Any advice much appreciated.