Thanks. I did not know they all looked the same.
If it was me, I'd drill a small hole in the lever and also each half of the broken knob not going all the way through. Then I'd mix up some Acraglas
and epoxy everything back together. The holes are for adhesion and strength.
This stuff is incredible. I have literally remade missing pieces from plastic and wood components. And it sticks well to every kind of surface.
More expensive than KA sending you a free lever, but this is handy stuff to have around anyway. Mix it in a plastic bottle top if you just need a little.