Push notifications on a hosted site

Hi, I’m using the hosted version of Ghost and I’m looking to install push notifications on my blog. I’ve used onesignal previously on WordPress, but that has a native plugin on there, and when I’ve tried to install it on Ghost I’ve needed to upload files to the root folder which I don’t have access to.

Could anyone recommend any way that either this could be done with onesignal or an alternative that would work with hosted Ghost sites?

Thank you