Check West Marine online, they have ignition switches. The one I have for my jetboat is an off-ignition-start type just like what's in a car. In addition, it also has a push-to-choke function, but having a 4 stroke engine, I don't need that feature.
I forget the mfg. of this switch, but I want to say it's a Cole-Herse.
For a kill switch, there are several made. The one I have has 4 contacts, 2 are NO (normally open) and 2 are (NC) normally closed.
The closed circuit is what completes the electrical loop, allowing the keyswitch to function as it should.
The open circuit stays open, except when the kill switch lanyard is pulled, this closes the circuit, and is the equivalent of someone hitting the stop button.
You'll have to sit down with a wiring diagram of your engine, and a VXOM meter, you'll need the meter to test continuity and such, to confirm that you have the switch correctly wired.