Crazy Crow also has German tanned buckskin, I'm not sure if it's actually "brain tanned" though,... as they have the regular and the smoked variety.
The Leather Guy has commercial smoked brain tanned buckskin, that is supposedly tanned with the the same chemicals found in animal brains and then smoked.
Both of the above are more economically priced than real braintan done the old fashioned way.
I use all three,... the German tanned, and the commercial brain tanned, and they are both better than chrome/veg tanned, but lack the exact "looks" of real honest-to-goodness braintan done by hand.