At my son's school, one of the wagons that the band uses for equipment
had a tire that was destroyed (13" x 5"). I offered to get a new tire
and replace it. The only store that has a good selection of those sorts
of tires is Harbor Freight and they have a big problem keeping them in
stock.
http://www.harborfreight.com/13-inch-x-5-inch-heavy-duty-pneumatic-tire-37767.html.
You have to buy a whole wheel, tire and tube, to get the tire, though it
was less than $10 with one of the ubiquitous 20% off coupons. Then I had
to struggle to get the tire off the Harbor Freight wheel. The wheel on
the wagon has a split rim and it was easy to replace.

Is there any place to buy just wagon tires for less? Seems ridiculous to
have to buy a wheel every time you need just a tire, and throw the wheel
away. I did a lot of Googling but could not find a source.