Not all archives are represented in the tools shown above. Some can be found using older printed "archival directories".
Use the library catalog, and search in keyword: [topic} archiv* director*
NARA has a website, but it is difficult to navigate.
Many researchers prefer to start with the Guide to Federal Records in the National Archives of the United States.
Before you travel to NARA, however, please be sure to contact the archives and determine that the collection you want is declassified and open for research. It may take a couple weeks to get a response.