Hi,
Not a 570 but I have a brand new M563 LX Rear Mech. Long cage, max cog listed as 32 (seems over cautious a maximum to me).
45 quid plus postage. It's what it owes me so I can't go lower I'm afraid.
Edit to add: sorry, if it's a 9 speed you're after this won't do. Ignore me!