Bought axle, wheels/tires from SuperSplit.
Bought the tongue, pivot (connected to tongue), turnbuckle ends from Kory. Something fabricators, that makes the Kory 3000, a 3k gvw, 4' x 8' nursery wagon that I use.
The steering knuckles are from a go-kart supply house. There is a spacer on the spindle. The go-kart spindles are nutted. SuperSplit spindle is cotter keyed.
Once I had the parts, a neighbor who has a welding shop, shortened the axle (making steer spindles match fixed axle width) and added the pivot/bushing in the leg for side to side pivot.
Relocated clevis holes in pivot plate for tracking. Replaced tongue bolt with removable pin. It all bolted up to existing four bolt leg mount holes.
I suggested to SuperSplit to offer a kit, or option, and they replied it would need brakes. I would think a wheel chair type brake could be applied.
One possible improvement might be to move the side to side leg pivot to the leg under the table, keeping the leg supporting the engine and flywheel weight ridged.