Made a proof-of-concept at work using a bit of cardboard and tape. And my trusty swiss army knife.
This leads nicely into
this
Took me 10 minutes to throw this together. I don't expect it to take much more for the real thing. All to scale, but not to the mm

View from the back plate with hole and tabs for the bayonet fitting of T10 connector (slightly covered by tape...)
Side view with "pipe" in between.
Front plate with cabochon...or bundle of tape...taped to the front plate

The hole is actually under the "cabochon" (see picture 1)
T10 connector in bayonet fitting and twisted to lock (yes I brought it to work...what?)
Ta da! For one... You can do a Rob and glue/weld 6 of these setups to the vent (only cost 22 a pair anyway). Or try to make one front-plate that fits using the stock screw holes...which is what I will try.