My church bought our Avantis from Sweetwater a little over 3 years ago. They were able to source the part when we needed to replace a fader bank last year. The other fader bank is now starting to give us troubles, so we contacted Sweetwater again. While I am not the point person on this request, my understanding is they don’t currently have any in stock and are having to wait for parts from A&H. I have not heard an ETA on the parts yet.
As far as replacing the fader yourself. It is super easy to do.