One of the companies that supply the RV industry is Topline Mfg.
I looked at the ladder mounts on their website and they look like what I have on our coach. They have a contact on the site and also a phone number listed.
http://www.toplinemfg.com/html/rv-un...lrvladder.html
Another company is Surco, But I am not sure if they made OEM ladders like Topline does. Here is Surco link:
http://www.surcoinc.com/RV-URVL.html