Very limited selection, if you need a free product
IME, you will have to pony up some cash if you want such a product that is truly feature driven. Most if not all off the free stuff is basically horrible. I would look at collectorz.com as a worthwhile, paid option. Your wish to have a unique catalog number may only be possible though when you export to your spreadsheet though. It's just not something most folks prioritize, with the exception of librarians (who I work with daily) .