You can't retexture a bat to look like a sword. Since it's only texture editing, the shape doesn't change, it would probably just look like a gray bat. It's impossible to do it well. However if you prefer to texture edit instead of model replacing, there is a wooden sword, used by vance in his pirate outfit. You could texture edit that and place it in the game.
If you want a more realistic sword, you have to model replace.