How to load Dropbox' dropins.js

I need to load this script:
<script type="text/javascript" src="" id="dropboxjs" data-app-key="my-api-key"></script>

I first tried to do a $(‘head’).append(’…’) on Template.Image.onRendered, but the problem is that the library loads every time the template is rendered, and gives this error: dropins.js included more than once

I’ve also looked at the wait-on-lib package,, but I’m not able to pass the data-app-key or id to the Router waiton function.

Do you have any suggestions on how to load this script?