I've been noticing ceramic supply house selling "kiln wash" like it's some mystery material, like the secret sauce on Big Macs.
Pretty sure the secret sauce is just thousand island dressing, and I'm positive that kiln wash is just this:
50% Alumina Hydrate
by weight. Or actually by volume will work, too - it's not that fussy.
For the professional potters among my readers - I know you already know this. I also have readers who are students or beginners, and I hate to see them wasting money on something so simple. If it's just you, mix it about the thickness of milk; if you are in a teaching studio, mix it more like heavy cream - students have a lot of glazing mishaps. Mix it yourself, and save your money for wonderful things like new ribs, or whoopie pies, or Bailey's Irish Cream, or whatever it is that makes you happy.