AESL (Aero Engine Services Ltd) don't exist as such any more, probably morphed into Aeromotives engine shop. Not sure they will have anything.
Try Colin Smith (Croydon Aircraft Co) at Mandeville, he's the DH guru over here but you probably knew that anyway.
There's also a very strong Tiger Moth club, someone there may be able to help.
Tiger Moth Club of New Zealand Inc