I've got the Cortech sport also and it sounds like it'll fit your bill. The cortech bag will hold a set of shoes and change of clothes no problem. It's got some nice features like expansion zippers, small pockets on the outside of the main section and a couple on the inside of the main section 'lid'
I don't use it too often, but when I have it's worked like a charm.
If you haven't seen it yet - TwistedThrottle
http://www.twistedthrottle.com/ is a good source for all sizes,shape and styles of bags from a number of manuf. Just some food for thought.
