Here is the PDF for the display.  It seems this rocker switch is connected between the transducer and display unit.  The switch is a Carling contura type, V1D1 and has 0244 on it but I cannot find that anywhere.
Boat is a 2003 Chaparral 215ss.

The switch had 3 positions.  Off was middle, up was lockable into place to turn the display on, and down, Im not really sure what for, also not sure if the down position locked into place or if it sprang back to off when released from down.  Actually not even sure what the down position was even used for.  The rear of the switch has the contacts numbered, and the contacts that are present are numbers 2,3,7, and 8.

Any ideas on the modern part would be?

That looks to be the same I installed on my boat.

When I installed it,. I don't recall anything unusual about it. My boat had a 2 position switch that I wired it to.

If you can find a 2 way that fits your console it will likely work.

Thanks!  I think this V1D2 1809 is prob what I need, even though niether group of numbers work.  but it has the exact correct contacts it would appear.

Do you know what the bottom position of the switch is for?

Sorry, no I don't. I have the paperwork that came with it somewhere but it's probably the same you linked to.

I can't imagine what the other position would be for. It's a pretty simple unit. Temp and depth. It does to air temp too, but that is switched in the unit itself so unless it was set up to display air temp when you held it down. That would be the only thing I could think of.