I don't remember offhand where the item text is located, but this document specifies the format that the letters are stored in:
http://jathys.zophar.net/supermetroid/kejardon/TextFormat.txt
Should be easy enough to find by doing a search for a string of the letters you're looking for in a hex editor.
http://jathys.zophar.net/supermetroid/kejardon/TextFormat.txt
Should be easy enough to find by doing a search for a string of the letters you're looking for in a hex editor.