@dannynu13 thanks for the info. i could only image this offline way: collect bargain book and save game. then quit and reload save -> bargain book is still in your inventory and perhaps there's another bargain book where you originally picked it up? this works at least for weapons and every other item in the game.
and something else came to my mind: this trick should apply to all magazines. so for example the mag that makes drinks last twice as long -> drinks last for hours. or something bad: psycho mag or s.th. like that that increases the PP bonus for doing certain things -> extremely high pp amounts -> leaderboards are screwed up.