So I know a few of you have got your hands on those internal ash pans from a Happy Cooker. From what I've seen on most of them...they are pretty rusted out and almost ready for recycling. Well...I found one and have the same issues with rust in the bowl part of it.
I found what may be an easy fix for that. What I used was an ash pan from a 22" kettle. I don't know what year this pan is from, or if there are variations on the outside diameter over the years. I placed the Weber ash pan into the Happy Cooker internal pan, and as you can see...this one is a darn near perfect fit as you can see. The vents of the internal pan are still open, and the Weber pan is the same shape as the bowl area.
Hopefully this will make some of your internal pans more usable now! Good luck.
And what a perfect fit!