have you checked speedway? i thought i saw some on there the other day when i was uh... doing research... (looking at 9" rears) i ran into the same problem as you're having in that i just was tire shopping last week. smallest 15" cooper makes for the cobra is the 215 and it's way too tall to tuck in on the early cars with stock rim/backspace. i've got aftermarket rims with crap back space, so was even more jammed up and pivoted in an entirely different direction.
anyway, since we're all spending your money may i suggest something like this?