your question is unclear.
Are you looking for outdoor speakers or outdoor speakers with built-in airplay?
If you already have an amp with airplay, it can receive airplay strweam and play it to a set (or two) of speakers. If the amp has speaker szone 2 or speakers B you can just get a pair of outdoor passive spaekrs and connect them to that zone 2 or B speaker output.
if you are looking for airplay outdoor speakers, then they only can be, as your airplay amp, an airplay receiver, not sender. i.e. you will not be able to send music to them via airplay from your amp (it has to be either from a computer with itunes or an idvice).
choice of airplay outdoor speaekers is very limited. there may be none. there are some portable airplay speakers that you can take outdoors temporarily (in fair weather).
most main speaker manufacturers make normal outdoor i.e. weather resistant speakers.