Hello @icheshire , I am not exactly aware of your development workflow.
But in the case of design manager and custom code workflows and serverless functions, You have to generate a bundle file and upload it to the place where you need it. There’s no direct way of uploading node_modules to hubspot cms because it is not meant for that.
Here is an example for custom code : How to Use NPM Packages in Custom Code Workflow Actions
Moderator note: While this solution may not address the original poster’s specific situation, it could be helpful for other community members facing similar challenges.