compact spare

The car has 15" 235 75 on it all the way around. I am just want a spare the same diameter to get home without breaking anything. I live in the middle of nowhere with almost no cell reception to call a tow truck. And I have a sure grip also. I did not even think about the spare until I was stacking the old 14's in the shop.

My Pirellis 235/55ZR17 are 27.2" diameter.
Yours 235/75R15 are 28.9" diameter.

By this id have to suppose my spare is about 27.2" diameter