I ended up ordering the pattern I'd posted about that Wallace Tire could get from the Specialty Tires of America company. They came in today via UPS with new flaps and tubes that I needed. The tread is really similar to the $50 Firestone tire that Coleman's shows listed. Figures something that looks the same would turn up for less money the day mine get delivered but that's how my luck seems to run
These were $135.91 and are 10 ply 7.50x10 made for a 5.5" wide rim. My towed mortar technically has 5" wide rims but I'm told there won't be an issue. Measured the actual rubber and its less than 5" wide at the bead so should bolt together with no problem and still have some room to expand when aired up.
My hard parts are being stripped this week but it might be awhile before I can get them painted and then mount the rubber. I'll update shots at that time though to show how they turned out.