Search ebay for keys. The seller of the programable key will have the sequence for you. I recently did this on a 99 Land Cruiser. I had to mash the brake pedal so many times followed by the skinny pedal then turn the key etc.... It worked like a charm and only cost me $10 for the key and $2 for the cut.
The best possible way to get a spare is the dealership. The key has to be programmed by someone else anways. It was either pay 60 bucks for programming with a no name key or get the infiniti key programmed by the dealer for 70 bucks. Might as well go dealer.
...Dealer wants $70 for blank key and $50 to program it...
That's B.S.! There's no way a key blank alone costs $70. When I got my 2000 I30t, I went to the dealer and paid a total of $65 for a new cut and programmed key. I would go back to your dealer and convince them that they're way out of line.