Here are the repos for MX Linux releases:
In MEPIS 7 and 8 users may need to edit /etc/apt/preferences file (as root) to enable the Community Repository packages to show as upgrades. Please visit the MEPIS forums and ask for help on doing this.
In MEPIS 11 and 12 (as well as MX-14), the Community Repositories have already been entered in your repository list, but are disabled by default. In Synaptic, you can enable them in Settings > Repositories by checking the boxes next to their entries – which will begin with deb http://mxrepo.com/