You can check the Computer History Museum's holdings on line. If they don't
have the documents already, they would probably like them.
The Living Computer Museum in Seattle had a working blit on display. If
they don't already have the manual, I'm sure they would love to have one.
Alas, their website says they've "suspended all operations for now", a
result of the double whammy of Covid and the death of their principal
angel, Paul Allen.