In Netsuite's REST web services help documentation, there's a reference to a Postman collection: https://netsuite.custhelp.com/app/answers/detail/a_id/86958/kw/postman
You can download the REST web services Postman environment template and collection of sample requests from the SuiteTalk tools download page at https://[accountID].app.netsuite.com/app/external/integration/integrationDownloadPage.nl. To access the page, you must substitute your account ID in the URL.
Note To access the Postman environment template and collection, the REST Web Services feature must be enabled, and you must have the REST web services permission assigned to your role. For more information, see REST Web Services Prerequisites and Setup.
However, when I go to the download page (with the correct account ID and REST web services permission), there's only a download available for "NetSuiteDataLoader.zip", which does not contain the postman collection.
Figured this out, a few pages deep in the documentation.
REST web services need to be enabled on the account first. https://netsuite.custhelp.com/app/answers/detail/a_id/87117
You also need to be a user with REST Web Services and SuiteAnalytics Workbook permissions. Administrator already has these, but if you need to add them:
Once all that is done, when you go to https://[accountID].app.netsuite.com/app/external/integration/integrationDownloadPage.nl you will see a link to NetSuiteRestApiSampleRequests.zip - which contains the postman collection.