Need Steal framing for door step support?

[pdxpfeifer]

So. Seems our back end is sagging and we have Dey rot and the steal framing that holds the step inside the door intoned the Rv rusted.  I noticed this weekend the bootm of my door was separating.  We were headed home and I stepped onto the step out of the RV adopt and it ripped off, luckily I didn?t fall.  The steal framing had rusted and broken in one side. The entire step was dry rot. All the wood issue the clipper walls appear to be dry rot. 

The seams of the fiberglass at the rear right behind the hot water heater section on both sides of the RV are separating the screws are just pulling out because they have no wood to attach too. So I have to fix that in addition to now having a huge gap in my floor.

Where do I get that steal plate to support the door floor?
Google photo link here: https://drive.google.com/open?id=17ZsxxhqeOZB8fIQVP10-3waDPcBb9ku_

[pdxpfeifer]

FYI - in case anyone else has this issue. I was able to have a new steel framing support for the back door fabricated by a local steel welding company, then had a welding friend help me mount it. The challenge is that the original screw bolts came from the top side of the RV when it was constructed and are in the wood coming down and then bolted from the outside.

This would have required me removing the furnace and the hot water heater, then trying to figure out how to drill down in those tight spaces. We decided to do large screws and drill up into the flooring, the screws are about 3" long? They seem to be holding well and I still have to finish the back and side wood framing that I had to tear out and then re-mount/weld the bottom of the door frame.