Running a spare tire, help!

Anybody know if you can run one tire different than the rest? I managed to get a screw in the sidewall of my rear right tire and Toyota say they can't fix it. I was just going to buy a cheap tire in the same size and run with that until the winter when I'll replace them all but Toyota says I'll have to buy 2 new tires now, and that running with the spare or a single tire newer/different or on a different rim than the rest can mess with the vehicle traction control system and make the vehicle's drivability compromised.
Does anybody out there have any experience with this? Or some wisdom? I really don't want to buy a full set of new tires yet but buying just 2 seems like a waste when they only have about 15-20% tread left before it's replacement time anyways!

Thanks

 

you really shouldnt but if you have to, run it in the front and dont put it in 4wd