Then why not try:
"Album Cover Art Downloader" (unrealvoodoo)
This one seems the most automatic, and will just get on with it when you "select all" and then click "download missing..." but has less sources (walmart, best buy, yahoo, but not amazon), and seems slower.
"Album Art Downloader" (sourceforge.net)
This one likes you to select and double click the image you want to be your album art, and seems quicker (but also depends on you responding to the prompts) and possibly more up to date than the top program, it also has more sources for album art including google images. You can also click "auto download and select artwork" which speeds up the process. It also lets you know how many albums you have without artwork, and then you can select them, and find artwork for them. Good stuff.
MP3TAG - universal tag editor (https://www.mp3tag.de/en/)
Batch tag editing, includes online database lookups, and the ability to rename files based on the tag information, as well as adding album covers. It can also create playlists if you want.
