The windcover you'll need will depend on what kind of hookah you have and what bowl you're using. If you have a Chinese or Syrian rig with a standard or even a vortex bowl, a regular windcover should be okay. If you have an Egyptian rig, you will need at least a large windcover. Add a phunnel bowl to that Egyptian, the only one that will work will be the XL.
Find out what you need first, then start price shopping.
FroYo = Phatt Azzd Kaloudz Yo!