Yeah, lappies are restricted in that sense... I have seen some with a 12.5, but it's rare as can be. That's why it will be sweet when a faster 9.5mm one will come out. If you want to use a 12.5, I recommend an external firewire enclosure. Also, if you are going to buy a 12.5mm drive and use it in an enclosure, you might consider looking for one with less cache and higher speeds (lower latency, lower access times, etc) because firewire and usb2 enclosures generally do not take advantage of the cache to the extent that direct EIDE or other connections do. If anyone has more info, let us know!
Habib