Can I create an NPM proxy for authenticated packages?

We would like to configure an npm proxy for obtaining a (third party) private package hosted on npmjs.org. By putting Nexus in the middle, our developers and CI environment would not need to directly configure that access, allowing Nexus to handle it through proxy and caching.

Typical access occurs, now, through local .npmrc file

@thirdparty:registry=https://registry.npmjs.org/
//registry.npmjs.org/:_authToken={theThirdPartyNPMAccessToken}

If I can create a thirdparty-proxy repository, within Nexus, that would handle pulling down the package (with token authentication), and include it in our current npm-group, this would simplify things considerably.

// this should get all the thingsā€¦

registry=https://my-nexus.server.com/repository/npm-group
email=my.email@server.com

I tried setting up an npm proxy like this, using the Preemptive Bearer Token authentication type and using the @thirdparty NPM auth token in the Token field (with and without the npm_ prefix) to no effect.

Is this even possible? And, if so, how?