Andrea, you should still be able to tan that hide, if it isnt too dry. Soak it for a few days in the brine first, and then go from there..
A good place to order allum is through Vandykes Taxidermy Supply in South Dakota. 1-800-843-3320. I havent done buckskin yet, but it is on my list!
When I used the feed store salt I found it was a little too course. Pickling salt works real well. (There have been times when that was all I had!)
It has been awhile since I did a search, but I think I did find alum online somewhere..... try potasium alum or ammonium alum, they both work.
Glad I had some useful info!
