I have also used the Stewarts on an old Tyco that I kept. They are much better than the stock rubber.
Note: Calumet Trains now sells this line. http://www.walthers.com/exec/search?quick=calumet&quicksrch_butt.x=23&quicksrch_butt.y=13
Jim
I see no reason that dental rubber bands won't work, providing they fit tight.
I was at the local Big Lots with the fiance a while back and found a bag of little black rubber bands the ladies use in their hair, it was $1 so I got a bag on speculation I might be able to use them, there were 5 different sizes in the bag and the smallest size is identical to the traction tires the LHS sells, so I tried some on an old Bachmann F7, works great! and they don't crack or wear out easily.
If you want the actual traction tires go to Walthers website and type 'traction tire' in the search and you'll find what you're looking for.