Humminbird Helix 12 Mega, which tranducer?

I am thinking about running a separate power cord and trolling motor transducer so I can get by with without having to add a 2nd graph. Which trolling motor transducer to I need?

The MEGA SI transducer that comes with the trolling motor mount is the
XTM 9 20 MSI T

I Forgot to add that I am wanting a down imaging trolling motor transducer not the side imaging

There is no DI transducer that matches the Helix MEGA SI circuits that I know of.