I purchased 2 6ft rectangular steel stock: 1/2" x 1/8" for $4.69 each.
Also, a #6 bolt , washer and wing nut for $1 .
JC sewed these green cloth covers, and secured them with bows.
The steel needs to be bent into a smooth arc, for which you will need a jig. I used a workbench with a couple of bearings bolted to it. I made the mistake of trying to bend this by hand, which put a couple of kinks in the metal. Once the jig was set up, I fed the metal through the 2 bottom rollers (pictured left) and bent it to the left of the top roller. When feeding it into the jig, The first bend made a kink in the metal, but at least it is the same for all 4 legs. The result was having 4 sections of straight metal on the ends, with the center sections having a smooth arc.
Steel will retain a camber with a curvature less than that of the jig you feed it through. If you can, increase the curvature with multiple runs. (I was not able to do this with my setup... since the adjustment knobs were maxed out with the exact curvature I needed.)
Here is the center bolt+wing nut. Use a drill bit with the same gauge as the bolt for a snug fit.
I wrapped the feet in electrical tape for safety.
If you plan on using this on wood floor, you will need to tie the opposite ends of the rods together. The downward pressure from gravity and baby grabs will cause the legs to spread out. Putting this on carpet creates enough friction on the feet.