Polymer Access node_modules outside of app root

I am developing a polymer website and an node.js server. I use the following folder structure:

Folder Structure Picture

I need to access a element from node_modules inside the polymer app, but I can't access the node_modules folder, because it is one layer above my app root.

My question is how to configure the polymer app to be able to access the node_modules folder from the polymer app with the given project structure.

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