It's definitely not going anywhere

from here and here (image source)

Sometimes you have to think outside the box. Instead of trying to prevent something, figure out an alternative where the thing you were trying to prevent is simply not possible to do in the first place.

Of course it's also a good idea to keep alternative threat models in mind too. No one will be riding off with this, but they could certainly carry it away, and that lock looks like you could just slip it over the top of the seat.