If you want to do this yourself start by creating a graph using Plotly, and then upload it to your Plotly account. Once you’ve uploaded the graph you can then get an embeddable iframe that you can supply as the popup argument in addMarkers().
I showed this insanity to Brooke and Roger, and Brooke mentioned that it reminded her of the artistic concept of mise en abyme (literally: placed into abyss), which describes the experience of standing between two mirrors. The next logical question for the three of us was: what are the limits of using an <iframe> in a Leaflet popup? How deep does this rabbit hole go? I uploaded my first map and attempted to embed that site into yet another popup: