I have some highly detailed maps of Southern New Jersey. This Garmin map covers the core area of the Pine Barrens.

Never got around to adding it to GPSFileDepot but you can download it directly here. It includes full documentation and installation instructions. Just unzip the file after downloading:
http://boydsmaps.com/download/core_pines.zipNot very happy with Garmin GPS devices anymore and prefer my smartphone, so my new maps are in a universal format that works on any kind of computer, phone or GPS. They are compatible with your eTrex, but Garmin has placed some limits on the use of this kind of map so you can only load a small area (regardless of the size of your memory card). You will have to install a free program called Mobile Atlas Creator to use these maps on your computer. Full step by step documentation is included with the download.
This map shows tax parcelsin the Pine Barrens:
http://boydsmaps.com/download/parcels_in_the_pines.zip
This one covers all of Southern New Jersey and combines aerial imagery with with LIDAR elevation data, showing details you would not normally see in the flat terrain:
http://boydsmaps.com/download/LIDAR_in_the_pines_2017.zip
I am currently finishing up a new topo with extreme detail that covers all of Southern New Jersey along with a large portion of Pennsylvania, Delaware and Maryland. Hopefully it will be available in June but it's a big project that I have been working on for a long time.

Regarding Garmin products, City Navigator is the new version of the MetroGuide maps - this is the same map that's included on their automotive units such as the Nuvi. They have one version for all of North America and another less expensive one that covers the "Lower 49" US states.
They also have a 100k topo map that covers the entire US, and a series of 24k topo maps that each cover just a few states but have greater detail and accuracy. They tend to be rather expensive.
A 32gb memory card is overkill for your eTrex, Garmin devices are limited in the amount of maps that can be accessed, regardless of how large your memory card is. In most case, you will exceed this limit after loading a little more than 4gb of maps. This limit applies to the small tiles (segments) that make up an entire map. You can only access 4000 of these segments on your eTrex, and if you exceed that limit, some of the maps will not work.
If you select an area of a map in Mapsource, it will show you how many segments are included (this is not so easy with Basecamp). So just be sure that this total stays below 4000. The limit applies to all the maps you install on the GPS, it does not matter whether you have enabled them.