I checked at Out of Doors Mart a few years ago for those same replacement parts. When they called, someone at Airstream told them those parts are no longer available. Either used parts or repairing what is there are the only options.
The bottom of the drawer in my 99 Excella is rusted out in a few spots and has flakey rust over the entire bottom. The fiberglass bumper cover is cracked from a slight collision by the PO. I have been contemplating this repair for 3 years, from the time I purchased. During that time I have not seen a complete drawer/bumper for sale anywhere. Though, I suspect any used one I could find would be in similar condition. I've decided to rebuild the existing drawer box, when the time comes that it does not function for me.
There are a few threads in the forum about how to rebuild the drawer box using the existing rails. I have not studied enough to explain that process.
This week I have been working on the bumper cover. I've straightened out the metal support structure beneath the cover and part of the drawer that was slightly bent (using a hammer, pliers, and a block of wood). I've removed the loose pieces of gel coat from the bumper cover. My plan is to fill in the small voids with a buildup of fiberglass cloth and resin. Then I will coat the entire damaged spot with resin. After sanding smooth, I plan to paint the entire bumper with truck bed liner, the type in a rattle can.
2014 Silverado LTZ 1500 Crew Cab 5.3L maximum trailering package