I guess you might be trying to avoid wiring and drilling hokes in your pride and joy?!
Understandable but I think you may struggle to find a handheld devuce with both functions because, as already replied, the depthsounding capability needs a transducer in the water, or at least glued to the inside of the hull to shoot signals through the hull into the water.
Handheld depth sounders do exist (you typically chuck a floating transducer into the water which the handheld connects to via a wire or with bluetooth) but in my experience they are pretty mickey mouse and i very much doubt there will be one with a chartplotter function.
Handheld sounders may of course have improved since my trials of them which in truth are now many years out of date - if they have you could consider using one alongside an ipad for chartplotting (or one of those dedicated sailing tablets that i have seen which look very fancy if a bit expensive)…
There is one other potential solution, if you are trying to avoid installing a transducer, which is to use a Chartplotter/Fishfinder combo with a transducer on a demountable bracket - the brackets are available for fishing kayaks and should be able to be tweaked for a small sailing boat (try Railblaza). You set the transducer up when you need it by deploying it over the side of the boat on its demountable bracket. You would still have wiring and need a 12v power source though which means some sort of battery in a box and more wires. I have tried this solution on my kayak and found it a PITA to deploy in practice so I just went ahead and installed a fixed shoot-through transducer with a battery box all located inside the hull.