Under Cab support rust
 

I have a 2000 F150 Supercab. Several months ago, I had it inspected and was told that I have rust issues under the cab which will be a problem the next time I want to get it inspected. The main rust seems to be the bars that run laterally across the bottom of the cab. I have been told that there are slide in replacements for this. I looked at LMCTruck but I don't see any parts there. Anyone have any experience with this problem? Where to get parts, custom manufacturing, etc....?