Cache busting a web-based Javascript plugin

So, I'm currently building a web-based plugin. The plugin is integrated to a site by including a JS file, say, for instance, www.example.com/widget.js is attached as a script tag in the customer sites. I need to cache bust this JS file when I have future updates.

I cannot use hashing in the name as the clients will have to reintegrate the plugin whenever there are updates. I cannot use versioning in the URL for the same reasons. Any strategies for this could be done?