[Kalzazz]

Most Amtgard ones are around 2.4in or so diameter for the blade (there supposed to be 2.5, but pool noodle is closer to 2.4), but bigger ones are absolutely possible

Also 'Flatblade' style boffer swords tend to be more properly sword shaped while still being fat with padding . . . you could absolutely disguise an arming sword as an Amtgard flatblade. You would simply build the Amtgard flatblade around the cardboard sleeve that goes over the swords blade

Wrap the grip in vetwrap or grip tape (which also conveniently makes for a good grip) and pad and tape the crossgaurd and stick a foam cover on the pommel

A cloth cover then goes over the 'blade' and ties down onto the handle of the sword (a real Amtgard sword would also have the blade snugly taped in place also, but that is less desired here)

In order to use it you would need to untie the cover (perhaps 2-3 ready actions), and then you would either need to spend another 1-2 actions to pull the flatblade off of the actual sword blade