Just bought a Boxster S at auction today with NO KEYS :(

[thstone]

There are no good or inexpensive options. As Particlewave said, its a $500+ problem no matter what you do.

Its fairly easy to get the physical key shank cut to fit the ignition switch.

The hard part is electronic where the transmitter inside the key fob, the ECU (aka DME), and the immobilizer all need to be programmed with the same security code or the engine won't turn over. Only dealers and a few independent shops have the test equipment to do this programming and they typically charge $250 - $400. And that does NOT include the cost of a new key.

PW mentioned buying a used matched (pre-programmed) set of key transmitter, ECU, and immobilizer and swapping them in but that will cost about the same as buying a new key and having it programmed to match the ECU and immobilizer.