I managed to buy stainless steel rods from Grainger and have them delivered. If you have a metal supply near by that is also an option. The cheapest way to cut the axels is probably an angle grinder with a cut off wheel. I was lucky enough to have access to a chop saw. If you are using it on stainless grab a fresh cut off wheel so it isn't contaminating the SS. Afterwards you can take some emery paper to sand it smooth.
Unfortunately SS is about the only material that is resistant to rust. The axel rubs too much for paint to not be scratched off exposing regular steel to the elements.