Search Amazon for "SD GPS SDG". It's a $60 GPS Bluetooth device that is powered by your SD slot (and provides a SD micro slot). I haven't bought it yet, but seems like a better option than buying a N810. It can't be worse than the reports from the N810 users.

Edit; good catch frasej. I knew it would stick out, and would mean having the kickstand open or removed. I didn't know the door had to be closed to recognize the card. well there are external options... that and it seems I have more to learn before buying.