1. Baking soda and vinegar. Make a paste with the baking soda and scrub. Put the stopper in the tub and then pour in some vinegar - the action between the acid and the base will clean up any remaining scum. There's no need for any toxic cleaners. I also will use Epsom salts as a scrub, since I usually have those in the bathroom for soaking for muscle aches.
2. If you're looking for something specific and can't find it through Amazon (who links many high quality 3rd party sellers for used books) or Half-price, you're not likely to easily find it elsewhere cheaper. I was able to find a used book authored by my great Uncle (and actually signed by his daughter) through Amazon. You might try eBay, but I think there you get into more iffy quality and less reliability.