I used a 3ft brass rod for many years. Stainless rods are best because they keep rust away. After that comes brass, then standard metal rods. You can get rods at most hardware stores (Lowe’s, Menards, Tractor Supply). Welding shops also carry rods 3ft rods. Also, McMaster-Carr online carries them. I’d go to a local store first—shipping is ridiculous on things over 30 inches anymore.
After flight, use a Scotch Brite pad on them, soaked with a little WD-40 or Sewing Matching Oil. Scrub the rods, then remove junk with paper towel and put a little oil on the rod to prevent corrosion until the next use. I bought a piece of 1” PVC pipe at hardware store and made a launch rod storage container. Put a cap on each end. Make sure one cap is removable
Come to think of it; I haven't cleaned my rods in ages. Probably just once in 4 years.
However, "this one time... at launch camp", a rocket took off and took the launch rod with it - the rod was pretty loose in the wood base so it didn't present much resistance.