Finally found a solution. Sno stuff makes a replacement wheel kit for these. They are non-pneumatic solid tire. $60 each but gotta have it. You would think they would give you a discount since their original product does not work.
surely you can remedy the situation for less than 120 bucks.
note to self don't buy any junk from sno stuff.
Seriously, I would start over. You mention the replacement wheels are non-pneumatic hard tires and they won't work well in gravel. You can find a new dolly with 10" inflatable tires for under 200 most anywhere verses 120 for something that may not work after all.
I agree with gary--Just get new and be done with it, then you'll know what you got.