Found it! Beldon did not have it, they sent me to a farm/feed store (after telling me that I didn't need lime and could just mix fireclay and portland cement... hmmm... don't think I will try.
In any case, I found powdered lime at the farm supply store it was $2.50 for a 50 lb bag, so that brings my grand total for the homemade mortar mix to a whopping $0.65 / lb.
I am still young(ish) and I have good insurance, not to mention all the friends who said they want to help... so hopefully there will be no hospital bills.
Thanks everyone for your input.
I keep meaning to get some photos of my oven up here, but have yet to spend the time figuring out how to do it.
If you are interested you can see some photos (although you will have to put up with other rantings and photos of things you don't care about) you can go to my website
the dan & carrie show
DAN