The simplest short-term solution is to call through Python using library(janus). That allows for interfacing to just about anything Python can in a few lines. If, later, you want to simplify the installation you can create a native interface. For Neo4j you may use the HTTP API, either directly or if there is an OpenAPI spec through the openapi pack.
Most of these problems should be fairly trivial these days
I was hoping I would not have to deal with HTTP myself, and I was also hoping I would not have to install and maintain Python on my Docker image, but it seems to be the only way yet