Replacing Sora crankarm
If you're replacing the whole crankset and BB, then any 9-speed double crankset should work. The chain width for 9-speed systems is the same for all makes (not the case for 10 or 11 speed).

But before you do that, I'd look around and see if you can replace just the left  arm. Any crank designed for the Shimano "outboard bearing" BB should work (those are the ones that clamp onto the BB spindle with two pinch bolts). Just make sure the crank arm is the same length.