Are there any other make/models that would have a used transmission (a Subaru perhaps?) that would work in my '87 (automatic, carburated, 2.0 engine) Honda Accord LX?
No. You need an automatic transmission from another Accord. No other transmission will work. Perhaps your transmission can be rebuilt. Why do you need a new transmision?
I’m dying to know why you don’t want to use a Honda transmission in a Honda vehicle.
In this particular case, you need to use a Honda transmission. There were a couple of models shared with Isuzu in the 1990s (Pilot, Odyssey), but they used different engines.
Difficult to come by