A tool that searches Launchpad PPAs via command line and adds them to the used repositories is PPAsearch. It may be installed on Linux Mint 9 (as it is Ubuntu 10.04 compatible) and on Linux Mint 10 (or Ubuntu 10.10),

To install this tool you need to open the terminal and enter the following commands:

sudo add-apt-repository ppa:wrinkliez/ppasearch

sudo apt-get update && sudo apt-get  install ppasearch

To search for a software PPA, just type in the terminal:

ppasearch software-name

You will see a list of PPAs that contain the packages and you may choose one by typing a number and confirm.

It is recommended to always try to add the official repository, the official PPA of the software.