Nearby where we are is an RV parts wholesaler that buys out inventory from RV companies that are going out of business. If you have a couple hours and a sense of adventure you can crawl around their warehouse and find just about anything. Check your area for something similar. There are online RV salvage yards.
My 2nd choice would be to replace them like for like. The reason being that they deteriorated once ... the next set will also.
My 1st choice would be to find a reputable fabrication shop and have them weld up something that will do the task. Do it once, do it right.
Our website: www.lifeinsidejack.com
Our Motto: Love. Joy. Hope. Peace. Freedom.