Dan,
You will need the item you've posted, as well as a barrel onto which the camera adapter attaches to. The barrel then screws onto the rear cell. From memory, you'll need an SCT adapter which screws onto the rear cell, too. Bintel should have all the bits and pieces. I sold my LX90 a number of years ago now, so can't remember 100%. Someone here will have more details.
Regards,
Humayun