There are WordPress plugins that have been developed to duplicate entire sites.
You can look into one of these plugins as an option to duplicate a WordPress/WishList Member site. All WishList Member settings, members, etc. are stored in the WordPress database. So, if a plugin creates a complete copy of the WordPress site/database, it should include all the WishList Member settings, members, etc.
We have not developed these plugins but we have heard Duplicator and WPvivid Backup are good options.
More details can be found in the WordPress plugins directory. There are a few different plugins available that duplicate / clone sites.