Have you tried using the same approach for installing scipy as discussed in the recent thread?
To get pip installations to work I had to use the full command from the Blender python directory including the target option:
cd your_blender_installation\python\bin
./python -m pip install “some\package” -t “path\to\blender\site\packages”
Tried installing matplotlib to see if it worked (note pyplot is a module of matplotlib) and it worked in the sense that I could import it in Blender, did not try installing Sumpy but hopefully you can get it to work.
You would need to repeat the process for the different Blender versions you are using though.