You don't need the exact same tire, just one that is of the same diameter.
There are several calculators on line that allow you to compare the diameter of sifferent size tires, try: http://www.1010tires.com/TireSizeCalculator.asp
My summer skins are 33x12.50x20" & my winters are 285/75x16", but both are roughly 33" diameter, so my 285/75x16" spare will work for either set.
Also, I got a used Honda Passport rim from a salvage yard for my spare.