Disneystore.com also carries some H2O stuff, look under the parks tab. They have the shampoo and conditioner they use at WDW for example. AND you can get them on sale, if Disney is offering any kind of sale like 25% off everything, etc. (and DS.com often has some sort of free shipping deal).
I also have purchased from the H2O site, and a few times from TJMaxx. TJ maxx today had the gift sets with the WDW products, in the same sizes they give away in the rooms, on clearance for $6 I think. (5 items in set I think)