Northern Tool didn't have anything I could use. Grainger has the same AGRI-FAB cart with 1" axles but replacement units are $54 each. The TSC web site and a phone call assured me they had them ($28.99) in stock in Beaumont. It took a 50 mile round trip to let them know that they indeed did not have them in stock.
"Will you sell me a pair off the AGRI-FAB 4 wheel wagon and replace them when you get them in?"
"No, sorry but it appears we have already sold them off the wagon.
I just emergency ordered 6 - 2 for you and 4 for us. Here's your raincheck."
"Why didn't you order 8 so you would have 2 in stock?"
"They won't let us emergency order normal stock."
I'm in the process of booting one wheel and tubing both tires. Yes, I said booting the wheel. It appears to have another valve hole.
They said they will call when the wheels and tires come in. It's still upside down on my trailer so pics of it maybe this evening. The kludge on the wheel will let me get it to the backyard.
That's a hard plastic boot I stuck in backed up with a 3 inch round patch you see, not the tube. 16X650X8 tubes were $11.92 + tax so I 'll pull them out when the new wheels arrive. Note that the tires still have the casting nipples on the tread. I don't know if the PO ever used the trailer.
The tires had been Fix-A-Flatted. It took a half can of talcum powder for each one to get the tubes in. Course, I had to dry them out, too. Heh . . . they didn't have enough water in them to weight them properly.