Jim informed me of a way to enclose the retractable lens on an Olympus C2020Z, using a filter adapter housing, a filter cap, and a couple of stackable filter rings (possibly with the filter removed) to get enough extension to put the cap over a fully-extended lens. These cameras use a motor to extend the built-in lens when turned on and retract it when turned off, but it's faster, easier and less battery draining to leave the camera on all the time with the lens extended, and let the auto-sleep feature conserve power when not in use. In the switched-on extended position, however, there's no way to attach the official lens cap. I think the built-in lens on my C3030Z has already taken rain damage.

What's worse is when you leave the cap (which latches pretty tightly to the base of the unit) on when you turn on the unit, and the motor rams your lens into the cap with horrible grinding noises. The C*0*0Z series has few design flaws, but that's one of them.

A link from that page: Digital Photography For What It's Worth, a collection of nifty articles, including some all about Olympus digital cameras.