The 3 links below are from around the country or Canada.Something you may consider.They either have parts or deal with John Deere.Either e-mail or call .You may have to look for "contact us" on the webpage. Since it is an older model....they probably...
John Deere is not the company they used to be. I doubt they have a tensioner and if there is it has little, little adjustment. If the belt keeps breaking clean you better bring it in for some warranty work. If it shreds everytime your working it too ...
There were in fact some John Deere tractors that were painted red but they were generally only for special industrial orders in the 1960's.