Not sure if this will help, but it might. I did a little research and what I found out is that it seems that TowMax are by Multi-Mile Tire Company. They are part of a private brand segment who's tires are made to their specs. IF what I found out is true, then this website might be able to help you.
TBC Private Brand Trailer Tires
Feed in your Zip Code. Then the miles you are willing to travel. Make sure no boxes are checked except for Multi-Mile. Not sure where this will lead, but it could get you closer.
EDIT NOTE: It seems that the tires savings link shows them as Sigmas
so you might want to check Sigma instead of Multi-Mile or maybe both?