A little clunky to setup, but works great because you have to set it up only once. This is how I did it:
1. Buy Keyboard Maestro ($36)
2. In KM Preferences check “Launch Engine at Login”. This way I don’t have to remember to start KM Engine every time I open Premiere Pro.

3. Download following KM Macro file I created:
4791_pptogglehand.kmmacros.zip
4. In KM select “File -> Import Macros…” then select the previously downloaded file
5. You’re done.
NOTE: The only downside is that once you release the space bar, the “Hand Tool” will switch to “Selection Tool” and not the tool that was previously used. This is ok with me because 95% of the time I use the selection tool anyway.
Also, once you import the macro file you can modify it in any way you want. I hope, though, that Adobe “fixes” this by allowing us to map this function within Premiere.