Chainsaw
I guess the chainsaw might be considered a broadsword. Okay, spec bonuses apply, but you'll have a -1 penalty on top of everything when using this until you've dumped another weapon or even a nonweapon proficiency in Unwieldy Weapons.
After several minutes, you can figure out the mechanism for starting up the chain... there's a small pull chain and a primer that needs to be pushed. Because I really don't want to have to do the math myself, I'll just tell you that this is a +1 weapon, and the chainsaw aspect adds another +1d6 to damage. You've got 2d12 rounds left of chainsaw goodness.
Another day of searching turns up nothing... the junklands is full of stuff, but everything beyond what you've already found is destroyed beyond use. There is lots of glass, for instance, but nothing that isn't cracked and broken.