I'm so sorry. This sounds incredibly stressful for you and the businesses you support.

While you're working towards a resolution with Heroku, it might be possible to bring up some of these apps relatively quickly on Digital Ocean's App Platform since it uses many of the same buildpacks as Heroku: https://docs.digitalocean.com/products/app-platform/build-sy...

This won't help in the cases that need data for proper restoration, but perhaps it'll get some the businesses you support taking reservations again sooner.

One benefit of having chosen a buildpacks based platform is it's easier to move than most proprietary or bespoke approaches.