Mkpass
Mkpass - Command line Secure Password Generator
... upon it.
https://en.wikipedia.org/wiki/Random_password_generator
This is a single executable JAR file. While you will need Java installed, there is no need to install this program. Just download the JAR file, please it somewhere convenient, and execute it from the command line:
java -jar mkpass.jar
See home page for additional details and usage instructions. https://github.com/frossm/mkpass