As I was completely tearing down and renovating my 1999 XJ, I decided I'd also refresh the evaporator (and replace a leaking heater core) so I ripped out the dashboard and started digging into the HVAC system. When I got to the evaporator and removed it (gently) the styrofoam insert beneath it cracked into 3 pieces. I first considered just carving one out of pool toy foam, or seeing if I could mold some styrofoam again, but found those options dissatisfying. I'm decent enough in CAD and own 3D printers, so I instead took the route of measuring/modeling the cheap piece of styrofoam and ended up with this 3D model. I have long since inserted the one I printed into my HVAC system with minor hand fitting, but I just remembered I'd done the work, and wanted to share it with anyone else in the community who might benefit from just letting a 3D printer do the work for them.

So here it is, a 3D printable evaporator holder. I recommend using durable/flexible materials. Mine was PLA, but I printed with walls thick enough to allow for minor hand fitting (which everyone will likely require if printing from solid materials). Another option would be using something flexible like TPU.

https://www.thingiverse.com/thing:6536124