The final step was to determine how to bring 19vdc into the TI-99/4A chassis.

Below is a shot of the internals where AC power comes into the stock machine from the standard brick:

I obviously did not want to reuse that connector, because someone in the future might come along and plug a standard TI brick in there.  It would probably not work and/or start a fire.

(I mis-spoke in an earlier log, it's not mains coming in, but it is a set of stepped-down AC voltages.  I will try to correct the log).

The solution I came up with was the design and 3D print a plate/bracket for a barrel jack sized correctly for my laptop supply.  I did find another maker out there with a version of this, but it was not a good fit.  This is the result, new on the left, original on the right:

This is how it looks with the case all buttoned up:

You can find the stl for that bracket here:  Printables