The best way to buy a tire like this is to take it off, bring it in the store, and compare it to theirs.
I've been told to put Slime in the tires for my wheelbarrow and hand truck. These smaller tires, as well as bike tires, do tend to go flat after a few months. They just aren't made to the same standards as car and truck tires.
Personally, I feel it's more trouble to put Slime, or those flat repair canisters, in the tires than to just pump them up now and again. A cheap auto compressor makes short work of it.
Pagan