Hyperflex? My US12's fit perfectly... try wetsuitwearhouse.com
ditto...definitely check them out
My shoe size is only 9, but the Hyperflex Amp boots are great (my booties have lasted over 3 years of regular use) and Wetsuit Wearhouse is awesome. I just got a new supply of booties, gloves, and other accessories - one of which is a Hyperflex poly fleece uni-suit base layer. I prefer the split toe high tops, some people like the full boot so you can wear a thermal sock underneath...probably warmer for the really cold water.
WSWH has a great staff for phone support. They have a toll free number from the US, and an international number as well. Worth a call if you have any questions. Ordering and return policies are very user friendly as well. They have board wax and wetsuit repair products as well.