Scotty and RAM both make fish finder mounts that will raise up the finder to a viewable level.
Ram:
http://www.kayakfishingsupplies.com/...m-mount/Detail
Scotty:
http://www.kayakfishingsupplies.com/...ost-272/Detail
use it with this to position it just about anywhere
http://www.kayakfishingsupplies.com/...ar-Head/Detail