Programmatically issuing organization access tokens?

We are currently considering using Auth0 Organizations, as a way to detach the ownership of resources from an individual, and instead associating them with the group. This + org roles have worked well for us so far, but the biggest missing feature is the ability to issue accessTokens for our APIs outside of a web browser, for testing reasons.

Is there a reasonable solution to this problem? I have found reproducing /authorization calls outside of a browser to be somewhat tedious and error-prone - in our non-org version, we simply call /oauth/token with username and password connections enabled, so we can perform full tests with real access tokens.

What is the best way to generate test tokens with org_id claims in them?