You can download additional boundary files here: http://public.goldensoftware.com.s3.amazonaws.com/index.html?prefix=boundary_mv7/.
Since MapViewer supports several commonly-used formats for geographic data, you are not limited to only using the files that we provide. There are many sources on the Internet where you can download additional boundary and data files. Some of those are listed on our Useful Links page. If you can't find what you're looking for there, try a web search on with terms such as "download boundary files", "download shapefiles", or "download gis data" along with your location name.
Updated October 10, 2016