I agree with Dons 1...2...3... as above.
I have read as well that I think that it was the company that makes cooper produces the MT as well (I could be wrong.... just going by memory from past topics read).
Here are a few links that may be of assistance. There are more to read if you search, but this will get you started for alternatives to what you have.
Definately (not maybe?) new 15" tires!! (Mickey Thompson Sportsman "S/T" ) - FFCars.com : Factory Five Racing Discussion Forum
Great Cobra Tires
Mickey Thompson