Like you say, these boxes are rare. Did you ever explore the possibility of using a UK GL 2.0 auto gearbox when yours went bust?
I ask because my decent car is a GL, I've done lots to it and so I wanted to turbo it. So that's why I bought this '94 WRX as a donor. But it's a real shed, in worse condition than I expected having been given the once over by Surrey Subaru Specialists who I took (trailered) it too for the ATF change. The car has a list of faults longer than my arm including HG.