Getting Metadata from Amazon

I get most of my of books from Amazon, and they seem to have the best selection (for ebooks) of metadata. By best I mean not only the data, but being able to use the initial data to do a global search & replace (for example, all the various forms of Science Fiction to "SFF__". Some parts of their data is just silly, and I periodically do search-and-delete on it [such as "Two Hours or More (65-100 Pages)," and it's cousins] I do a lot of editing on metadata, and have a lot of custom tags, but in many cases I'm dependent, at least initially, on the original Amazon data as a starting point.

However, the metadata for IDs that is returned (i.e., mobi-asin:B01M33A032) has a very poor record of finding the correct book from Amazon when I hit [Download Metadata] ==> considerably less than 50%. It will bring back the wrong book, no books, or the book in dead-tree version, which normally has little metadata.

However, if I manually put in "Amazon:B01M33A032" in the IDs field, my success rate goes to 80% - 90%.

So, is there some script or add-in available to do this automatically on a selected subset of books? With 500+ new books from the recent Open Roads giveaway, I really don't want to do this manually. My goal is to select the 500+ books, run a script to add the "Amazon:B0xxxxxxxx" automagically, the use [CTRL-D] to download metadata only and get the correct Amazon ebook metadata most of the time.

Thanks.