I have found a way, as I am sure others have, to get a GI type cut. You have to set your mower to the lowest setting. I don't like that look. Like when my grandpa used to cut my hair in the summer with those clippers after convincing my mom he had done it once in the navy while overseas with his drunken buddies. I cried less when my dog died. (I guess I was pretty vain even as a child.)
Craigslist is the place to find these mowers. I have 2 of my friends now mowing this way. (oh, and I only have 3 friends) My mower is the nicest of the bunch tho.