There have been times when the lens on my camera was not the lens that would have been ideal... too long, too slow, too short; but the time to switch to the ideal lens allowed the moment to slip by. I had read of someone else's solution found here
blog.tonyschreiber.com The Best Two-Camera Strap Setup Yet - Part II but was hoping that there might be something ready-made and affordable.
I think I found something that's very affordable and seems to work pretty well...
Amazon.com: Op/Tech Bino/Cam Harness, Elastic Version for Cameras & Binoculars - Black: Camera & Photo
basically, instead of hooking both clips to each side of a camera, I hooked each clip to a camera so I then had two k10's, one at each hip. I tried it out for around a half hour walking around my house, and it was reasonably comfortable. the straps of this harness are elastic, so I was a bit concerned that the cameras would hit against each other if I was too careless (it would actually take a pretty hasty twisting movement for this to happen, but I just wanted to reduce the possibility). So on one side, I used an extension strap (optec seems to use the same clips for their neck strap, extension straps and this harness)
Amazon.com: Op/Tech System Connectors, Pro Loop - 14" Webbing (9 - 12" Each side): Electronics .
moving the camera up and down on the right side was no prob, but w/out the extension on the left side, I found the strap crossing uncomfortably across my face. but with the extension piece the strap wasn't as annoying. One thing that I liked about the "tonyschreiber" strap mentioned above is that he used something to keep the cameras from sliding too far down... basically some kind of stopper on the strap that kept the cameras from sliding toward your backside, making the cam a little harder to grab. also, the part of the clip that slides up and down the straps seems to be a bit tight and after a while, I'm sure the strap will begin to fray at the edges. but for under $30 shipped, this is a decent solution if you have 2 bodies and want to be able to have them both at your side.