There is ONE company that makes one, but it's tiny (25 gr?) and costs 900 yen...so it's pretty much the same.
Alum is VERY water soluble. Dry it and store it someplace away from water...I didn't and mine got all spiny and scratchy.
BTW, I use one as deo and I just crushed it, put it in a spray bottle and filled it with water. Now I have super-saturated alum water on demand...goes a little faster, but super convenient.