If anyone else is trying to do this, this is what I ended up doing. First get a 1 3/8" step drill and two 1 3/8" access hole plugs. This is what I used:
Opening up the hole in the back is easy but the inside is tricky because of the refrigerant tube. I removed the top two screws and loosed the bottom two in the cold plate. That let me pull it out enough to get the step drill behind it. Once you get the hole all the way open, move the drill around inside the hole a bit to clear out some insulation around the edge for the grommet to go into.
I used 1/4" ID and 1/2" OD gas tubing because it's pretty tight. I drilled two holes in the grommets and ran the tubing through that. It was a bit of struggle to get it together but eventually I got it.