Below is a link to an ebay auction selling a remote key head that may or MAY NOT work on your model year Boxster. You'll have to call the parts counter at your local dealership to get the part number right and then match it to the picture in this auction...
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=40016&item=7956234014&rd=1
If your part number does not match this one, then pass it up... but if it DOES match, whoo-boy you'll save some dough.
What's good about this auction is that this remote key head has
the original tag on it and this is the ONLY way a Porsche remote key head's transponder can be programmed or reprogrammed.
I bought one about three months ago from this Ebay seller and then ordered a blank for my car through the parts counter and had the dealer program it. Saved well over $100 this way over just asking the service department to order the key parts and do it for me.
(Don't be fooled by the morons selling used Porsche keys on Ebay as they are totally worthless...well, not
completely worthless... if you want to give your teenager a key to your Boxster for Christmas that won't work, this is the least expensive way to do it!)