Will has kindly set up a small CDN for us to host the old map files publicly. The map files that we still had around are already available for download. Moving forward every sdot and modded map will become available for download shortly after they have been retired. A word of warning, some of the maps are quite large so be prepared for a long download and take note of the size, especially if you have a data cap on your internet from your ISP.
You can either go directly to https://cdn.mcnsa.com/archive/ or if you are already on the main MCNSA website you can click the "Old Maps" option on the top right and that will take you there.