>You need to get a towel and put it on the opposite side of the fabric, get the bottle of hydrogen peroxide and pour some onto the stain, and dab with another towel.

To add to this, the stain can bleed (woops there's a pun) into the towel you use so use something appropriately colored or that you don't care if it gets stained.

Or eBay, thrift stores, etc.

USPS has media mail rates meaning I can frequently find very specific books for like $5 total online if they are older.

Also for finding something random I love just taking the time to go through that hige wall of books at a thrift store to dig out something that looks interesting. $1 or $2 per book usually.