It'll fit in a duffel bag...won't be able to lift it easily though lol...I love this idea, as well but when I did some more research it's highly recommended against my car (Genesis Coupe 3.8 ) towing anything behind itA 140lb trailer and a CBR250R doesn't add up to much weight...I may be overly paranoid about it but not sure.
I'm not a mechanic.. but I don't think you would have any problems towing a CBR250 on a 140lb trailer behind your car.. any bike for that matter..