The cheap and 'risky' solution:
DIY: Making cheap spare keys
I have done this to four Boxsters, two of which I sold and explained to the buyers. They were buying at a good price and happy for the extra keys.
While I understand that a pro or a purist would find it to be a cringeworthy solution, to those who own Boxsters as a fun, depreciated car it may make sense.
***I may have mis-read your post. You will need at least one correct key-transponder to make this work.
This glass pill thingy: