Hi Kibarn,
I got my fireclay from Deering Lumber in Melrose Ma. I think it was a 25 pound bag. (small bag) I don't remember the price but it was pretty inexpensive. I don't know if you're planning to cut your firebrick with a brick saw or if you've done it already, but to tell you the truth, you don't need fireclay if you can use the 'sawdust' in the wet saw pan. It's basically the same thing. I ended up buying the fireclay only because I had chunks of brick in the wet saw pan. If you pour the wet brick dust through some sort of strainer, (kind of like panning for gold) you would have more fireclay than you'd need!
Rick
Come to think of it, (now that I already wrote this

) I don't know how far you are from me but you could have the rest of my fireclay if you want. If you're interested, I'll have to check how much I've got left over. Your welcome to it!