The Demos folder has wma but not the Soloists or Styles, the other demos are in c:\bb\Realtracks\Data
Songs and Lessons has wma
If you just do a search for wma in the bb root all the wma will all show then when search complete you can select all and drag into the Reaper batch encoder with it set to a new drive or folder keeping the source file directory structure.
I tried one file and it save with the extension mp4 but you need m4a so you will need to Bulk Rename.