On one occasion, I had a stick of wood get wedged in between the rim and the bead of a rear tire. I was fortunate I was able to get the tractor on an equipment trailer before it went completely flat and transport the trailer to a local tire shop that sells Ag tires. Fairly easy fix.
On another occasion, I had a front tire on a compact tractor go flat (if I recall correctly, it was a bad valve stem but I am not sure at this point in time) and I dismounted the tire and took it to the above mentioned tire shop for repairs. Again, a fairly easy fix and not expensive in either case.
If the tires involved are of a manageable size, you might consider dismounting them and taking them to a tire shop that deals in Ag tires and ask that they install tubes. If the tires are too big to manage, if you have an equipment trailer or if you have access to an equipment trailer, consider taking the tractor to the tire shop for tube instillation.