At selected Harris Farm stores this weekend they are selling Lady Finger bananas for between $3.99 - $5.99/kg.
I checked through all of the specials PDF's and it's only listed at the below stores:
Bondi Junction - $5.99/kg
Broadway - $5.99/kg
Cammeray - $5.99/kg
Dee Why - $3.99/kg
Manly - $5.99/kg
Merrylands - $4.99/kg
Mona Vale - $5.99/kg
Mosman - $5.99/kg
Pennant Hills - $5.99/kg
Willoughby - $5.99/kg
I don't know the difference between Lady Finger and Cavendish, but Mr Google says that they're smaller in size and a bit sweeter in taste.
good price compared to other stores
Aldi in Queensland (where bananas were invented) had them for $8.99 for regular, 9.99 for lady finger.