Does this pack come with a magnetic chest...
Does this pack come with a magnetic chest strap for the bite valve to clip on to?
Are you putting a new reservoir you purchased separately in it? Those come with sternum strap clips that make them compatible.
Or are you putting a reservoir from a Manta/Raptor/Viper/Verve in? If this is the case, Osprey makes a 3 magnet kit that you can put a magnet on every pack you'd switch the reservoir into that isn't originally a hydration pack...