2011 Prius with Rust underneath...

Hi all. New guy here. We have owned a 2010 Prius for about 5 years. We just bought a 2011 for the other daughter. We are in Florida, but the new one lived the first 5 years of its life in upstate NY...hence some rust underneath. Pinch welds mostly...nothing too bad, except for one thing near the back right in front of the rear wheels. There is a stiffening member that runs from side to side, like a round stock pipe that I would almost think looks like an anti-sway bar, but I don't think it is an anti-sway bar. Anyway, it is rusted enough that it is splitting down the center in a few locations. For the life of me I can't find that part so that I can get a read on the cost to replace it.

If anyone has any idea of what the part may be, let me know. I'd seriously appreciate it.