Try one of these:
I paid 11.00 plus $3.85 for shipping.
It handles 15-20 volts 3 amps.
I use it with my homemade 3 cell charger. Works great, and you can field charge with it in your car (use your tile box)
The seller (livbyfth) isn't offering them right now (as of 10/2), but e-mail him to see if he'll sell you one, or will be listing them soon.
A 12 volt power supply, despite the amps it'll deliver, will not get you the voltage you need. Most wall-wart power supplies won't supply the amps. Radio shack has a 12v wal-wart that delivers 14 volts no-load, but it only delivers 1.5 amps for $19.99. OK for small packs.
You need at least 15 volts, and 1.2 amps. If you decide later to get a 2100 mah pack, you'll be glad you had the 3 amp laptop PS.