It appears to me that you don’t have a neutral like you suspect. If that is the case your neutral is in the overhead light box. One recommendation I’d give is to find out if that other 3+way switch in the dual gang box has a neutral at the other switch. If it does, you could replace those with a GE switch and add-on and bring a line and neutral over with the existing wires.
In any case if you choose to use a GE switch or any other smart device you’ll need to rewire the light box as well. So you might want to verify the neutral is there.
If you can’t bring a line and neutral over your only option without running additional wires would be to purchase a relay and put it in your light box. Your existing switches would still work.
Here’s a reference. I’m guessing you have “power into light”