I wrote a couple of custom scripts based on Florian and Dano's Amazon cover art script. The first grabs the Album Art and ASIN from Amazon, writing the ASIN to the "usertext" field. The second only changes your usertext tag to the ASIN, which I use for albums that I already have art for but no ASIN.
One tweak that I made from Florian's script is that by default this one searches based on both artist and album title -- I don't know how many times I had to type the artist name into the search field before I learned to change the script myself. (There are too many albums by different artists that have the same name.)
Amazon_Cover_ASIN.src (3.29 KB)
Amazon_ASIN_only.src (2.94 KB)