I've come to the conclusion that a "puck" style TM transducer is not available for this unit.
This site says it will sell you a Navman 4430 w/TM transducer:
http://www.cascadegps.com/store/prod...?productid=535 ... for $117 (but fails to show transducer, or give details about it)
But, this site: http://www.navman.com/marine/product...ders/spec.html ... shows no such option available. Only transom, in-hull, and thru-hull versions are listed here : http://www.navman.com/marine/products/transducers/
However, depending on what type of transom mount transducer you have for this unit - it may be possible to attach it to the TM. It may have to stick out to the side ... and you may have to make sure and mount it on the side of the TM head that is clear when TM is stowed (up side). luck2ya ...cp