Instructions for gaining access to a Reatta with the keys locked inside:

Use screwdrivers to carefully pull the top of the door window away from the roof.

You must wrap the screwdrivers with something to prevent chipping the paint. Be careful pulling back the glass so you don't break it.

Bend the end of a small steel rod, then use it to press the power door lock button.

Thanks to Jim Finn, member of the Reatta forums, for this information.