external oxygen port?

On our way home not long ago we landed in Denver with our oxygen
getting low. I asked for a fill and they gave it their best shot
but our configuration didn't leave them sufficient space for all
of the adapters they needed to use. The ride home was...well, I
was glad that I had the oximeter. (As we went over the
Mississippi my wife couldn't think of the word for barge. "Give
me your finger!")

I'd like to make filling the O2 easier - especially when I've got
the rear baggage compartment loaded to the gills. An external O2
port seems like an answer. Another possibility is to have a more
standard port (than what we have now) that's located on the
ceiling or back wall just inside the baggage compartment door.
If I had something like this I think I'd finally get a couple of
O2 tanks for my hangar. That would make me more likely to have a
full charge when I need it.

Any ideas on installing something like this in an Aztec?

Thank you.

--kyler