Here's something you can try..

Keep your MP Navigator 3.1 installed (for now)

Install the MP Navigator 4 from the link canon asia link above

go to Applications/Canon Utilities

Right click on MP Navigator 4 and select "Show Package Contents"

Navigate to Contents > Plugins > Database

You will see a bunch of .plist files -- these correspond to the scanners that the asia 4.0 version of the app supports

Right click on MP Navigator 3.1 and select "Show Package Contents"

Navigate to Contents > Plugins > Database

You will see a bunch of .plist files -- these correspond to the scanners that the us 3.1 version of the app supports

Copy the files from the 3.1 database folder to the 4.0 database folder

Now when you start MP Naviagor 4 it will launch correctly and find your scanner.

I have not analyzed the contents of these plist files so I'm not 100% sure if this will work, but the contents of the files in the 3.1 version look pretty similar to the ones provided in the 4.0 version.