Q. Where can I find a chart or map showing population density of Duval County/Jacksonville?

You may try the U.S. Census Bureau Data database.  You can also find a lot of numbers from various Census documents and demographics websites.

The Consolidated City of Jacksonville Duval County, Florida Comprehensive Emergency Management Plan 2021-2025 contains a table listing populations by city region (i.e. Arlington, Beaches, etc.). You can use that data to create a table and charts/graphs in Excel.

See page 15