Are you by any chance using the free edition of DSS? If so, this would explain why the connector is missing as NoSQL connectors are only available in paid editions of DSS as can be seen in the following chart here:
When I'm not at work I use the community edition of DSS on my laptop. If you are looking for a database that you can use with the community version of DSS. I've been using PostgreSQL on my personal laptop for years with DSS. It's not a document database as MongoDB is, but if you are just looking for a database to work with on the Community edition. It's pretty good.