React Native Expo with Bugsnag Sourcemaps bugsnag-eas-build-on-success Not found

Question

I am trying to get sourcemaps to work on an expo 49 project.

the bugsnag docs say to add this to package.json

  "scripts": {
      ...
      "eas-build-on-success": "npx bugsnag-eas-build-on-success"
  }

However whenever building via $ eas build -p ios I get this error:

404 Not Found - GET https://registry.yarnpkg.com/bugsnag-eas-build-on-success - Not found

I've searched yarn and npm and this package (bugsnag-eas-build-on-success) doesn't seem to exist. Any help would be greatly appreciated!