Permanently swapping option and command keys on a non-Apple keyboard
I have a Logitec K750 and it has the left Alt key closer to the space bar than the Windows Key (to be used as Command Key). How can I remap the keys on JUST my Logitech keyboard and NOT on my built-in MacBook keyboard so that the Left Alt key functions like the Command Key, and the Left Command Key functions like the Left Alt key? Is there a way to do this without having any apps running in the background, like some kind of key-map file I can edit rather than using a tool to do it? I'm a real resource-conscious user and don't want anything running in the background.