I have seen both Hotcams for like $220 shipped from woodward specialties, and www.sweetquads.com. They run specials once in a while and some also offer discounts to site members on other sites

The only thing I have have aginst hotcams is their weight, the added weight of a hotcams upgrade will put about 47% more stress on your Zs timeing chain over stock. If you do a basic hotcams, DRZe base gasket, and springs upgrade its a good idea to slap a D.I.D HD timeing chain in there as well. They are only about $40 I think and are normally avaiable on ebay. Another maker of cams are Web, and also Yoshi has a racing grind for the Z as well I belive but for the money Hotcams is the only way to go.