Lss-1 or Lss-2 if compatible.
This will give you side scan and down scan imaging.
You will however need the structure scan box for it all to work together.
Do you have Gen 1 or 2? Gen 2 touch doesn’t require the structure scan box as it’s built into the head unit.
You will also want the HST-WSBL transducer. It will provide your speed,temp and 2D sonar as the LSS1 does not provide the speed and temp (I don’t believe).