I know it might be tougher to find now, but the Burton C60's are stiff as $%^&!!! If you want a small (sz 8 or less) or large (10+) there are white ones for sale by a few online vendors for roughly $280.
The highbacks are carbon fibre with an FRP structure behind it. Very stiff. I love them... Planning on pairing a set with a Kessler board if I get my hands on one.