Alright, in the US you can usually get 12in Silent Spinners, and 8in and 12in Comfort Wheels at any pet store, along with the 12in Flying Saucer. Silent Spinners are a favorite, but Comfort Wheels are much cheaper, but they also tend to be much noisier.
Online, You can get Wodent Wheels in 8 and 11 inch. eBay and amazon both have them, and several independent online retailers do as well. The price tends to fluctuate, so you may want to shop around if you decide to go for one of those.
Another online option is the Carolina Storm, 10.3 inches, which is what I use. These are handmade by a hedgehog breeder in North Carolina, but if you're concerned about space it might not work for you, as the base is enormous