Removal of A/C-heater box?

I am dealing with the same issue. Heat/a/c has been removed. I don't want to patch so to speak. Upon looking into 3D printing I keep getting pointed in different directions. Researched rubber grommets and they guy quoted $800 for the tooling alone. Of all the grommets out there it seems nothing fits closely. It would be nice to have a body plug to pop in on these 2 holes.
That said, I am left with 2 options. I bought "Versamold" online to "make your own" as seen on "Gearz" I have yet to try it. Or, bought some large size grommets from big rig websites for some type of truck parking lights. They are somewhat flexible but you have to cut in the middle and remove material to fit, then I used super glue for rubber to mate the ends together. I have done the heater section and somewhat pleased as an alternative to patching it. They are about 6-10 dollars each and through trial and error I went through a couple pieces. I am down to one piece to modify for the a/c hole.
Does anyone else have any suggestions?