USB to serial adapters do exist, take a read of this:
http://www.andybaird.com/qt200/cables.html
...but I doubt you'll be able to find modern software to pull the pictures off the camera.
Perhaps go searching for a first generation "Kanga" or "Wallstreet" PowerBook G3 (the series with the colourful Apple logo, not white), and hook it up to your modern machine via Ethernet.
It would probably set you back the same amount of $$$ as an adapter would.