Updating this because I have some info that might be useful to others:
Stopped by NAPA today....the guy at the counter, who happened to be a Jeep guy, found the part and said that they have both the disconnect and t-case vacuum pots in stock, but......they are in the process of renumbering the stock, so until the parts are relabled, they cant be found in the warehouse. He said to check back in a month or so. This particular NAPA is attached to one of the West Coast NAPA warehouses, so I expect he will come thru for me should I need a new one.
In the mean time, I got under my car and took some stuff apart....I thank my dad for making me help him build the grease pit in our shop in the 70's: Sure makes the prospect of getting under the car a lot more pleasant in the winter when the process doesnt include laying on cold concrete.
Anyway, I removed the Axle disconnect vacuum pot and bracket. I left it hooked up to the vacuum lines and started the engine, then moved the switch to 4wd position: no movement on the disconnect actuator. I moved it back and forth by hand under vacuum and it moved to the locked position. I disconnected it from the lines and worked it back and forth quite a bit and reinstalled the lines with the unit still removed from the axle, trying the switch again...it moved like it should, it seems it was just hung up from lack of use.
However once I got it working I still didn't have 4wd, so I looked at the connections at the T-case and found the one for the vacuum actuator loose on the unit. I cleaned and reinstalled the connector with zip ties and after that, all works as designed.
I think I will still replace both of these actuators while they are still available. Since the first ones have lasted 32 years so far, I think I will be more interested in my jetpack by the time the new ones fail.