The one store that might have had some, AllMac.com, is out of stock and will be for a long time (I contacted them and checked).
I wish I'd known - I would have bought up as many as I could back when they were still available.
In the meantime, you have one of two options - you can either wait and pay a lot on eBay for one (if you're lucky enough to find one for sale), or you can solder the wires directly to the pins on the LCD's connector. This isn't terribly difficult if you're patient and have a steady hand (the wires are a fairly fine gauge, but it's not unmanageable IMO).
You could also pick up an LCD cable for a different laptop and splice together the wiring from the old clamshell cable.
There are ways around it - none of them are as elegant as using an original cable, of course.