farm supply store will have what you need and hard tire wheels they also
should have a replacement tire or a insert made of hi density foam
rubber that still acts like a pneumatic tire and they usually have
different size tires to fit your needs also check out harbour freight
they usually have a selection of wheels there .
I did see someone build a torch cart using the old hub and wheels off
an old bug and keep air from leaking out you can try some green slime
for lawn and yard tires to protect it from small punctures
good luck