It would help if you have the AC make and model. You'll likely need to remove the interior air distribution cover to find the plate with that information.
Walt
Sorry, I misread. Ignore the above. I did google it, as I suspect you did and there's not much help out there.
I have a whole pla-cool unit off an old Terry travel trailer, poor shape overall but the roof cover can be repaired pretty easily. PM with your email addy and I can send you pictures
pictures sent, if this looks like your cover let me know
it would be enough to use as a model for a sheetmetal shop to go by, the water sprays down on the cone as you can see in second picture----other than that it is just a shroud to keep it watertight