I might get a chance to go to some fun events to take pictures soon, and I'd rent a lens or two to take with me (as this doesn't happen enough to justify buying a decent wide angle). However, this is an event situation, and I'd like to be able to switch between the lenses quickly. Thus, it would be nice if I had some way to carry 2 lenses, in such a way that they could be swapped out on a camera, without having to find a table somewhere to set down a traditional "backpack" or similar. It doesn't need to have space for the camera itself; that'll be attached to me via neck strap.
Does such a tool or bag exist?