Be carefull when doing that because some helmets do more harm than good...
Rick had many subjects here and in in the wyhoo newsgroup about protection gear. I can remember one with a lot of exemples of helmets not to be used for kiteboarding but cannot find it anymore.
I'd avoid the Capix helmet. I own one and I think it's almost worthless. It's a cheap helmet and you get what you pay for. Also, it has a "bill" or "rim" that can potentially cause whiplash although I just looked at their website, http://www.capixco.com/ and I no longer see that design.
I nice moderately priced helmet is the Pro-tec Ace Wake. The top of the line helmet seems like the Prijon Protector.
I'll probably buy the Pro-tec Ace Wake in the spring unless a better moderately priced alternative is released to the market.