Firstly, I said their CD is text-searchable; actually I don't know that for sure. Some of their CD-ROMs are searchable, some are not. But they are the complete books, including the index.
Secondly, don't rely entirely on their online menu to find what you want. In fact I looked for the Strang book that way and couldn't find it. You have to email them or call them and ask for it specifically. Almost always they can sell you what you want.