Samsonite wheelie case. Check their website - they'll tell you which one is the standard size that fits in overhead compartments.
You can then consider a Samnsonite laptop bag, whch has a 'sleeve' that slips through the handle on the wheelie case, allowing you to attach the laptop bag to the case and wheel them through the airport with one hand. Won't get your suit jacket creased with carrying it on the shoulder strap, and leaves your other hand free to browse duty-free.
Or you can go for the size down from that, but you'll have to leave your jogging shoes at home.
Do people actually carry a spare suit with them when travelling out of town? I just have the one I wear on Monday morning?