Geofencing Custom Audiences on Facebook?

In need of a way to leverage a KMZ map file to target a specific audience on Facebook. Anyone have experience with this?

Facebook had a tool called ISPToolbox. You can still find the website/pages online and even upload your custom KMZ or text file to plot on the map, or you can draw a custom geofence. It will allow you to choose an Ad Account, Audience Name, and Description. However, the “Create Audience” button does nothing. Upon investigation, they announced this past spring they were winding down the tool and no longer supporting it.

I really need a way to create custom audiences based on detailed service area mapping. A radius does not work for our clients, who are rural broadband providers and need the precise fencing.

Any ideas, tutorials, resources, or tips?