I bought a cheap leather band on Amazon to wear when I am on the elliptical. Still not ideal, but it was the only one that was available with the adapter, to ship right away. It's way bigger than my Apple band, so I roll up a thin sock and stick in under the strap on the underside of my wrist, so it can get the heart rate.
would rather have a sports band, but this will do for now, to keep my Apple leather band from getting nasty.