Not sure what adapter you are looking for. AFAIK, there does not exist an adapter that will permit you to connect your DVI port to a mini-displayport (or mdp) on a monitor.
You will need a "converter", not an "adapter". Specifically, one that will convert the DVI signal to a displayport signal. Displayport is not compatible with DVI.
All the items called "adapters" out there (typically called "mini-displayport to DVI adapter") will allow you to go "from" mdp on a computer "to" DVI on a monitor. They will not allow you to go "from" DVI on a computer "to" mdp on a monitor. The reason for this is that the mdp port on most computers are what are known as "dual mode" ports. That is, the mdp can also transmit a DVI/HDMI signal. There is no such "dual mode" feature with a DVI out port.
You must "convert" the DVI signal then use a standard DVI cable from the computer to the converter and plug the mdp cable from the monitor into the converter.
The converter I linked to above was only good for the 24" Cinema Display at that time - don't know if it will work on the 27" Cinema displays or not. Geffen was purportedly working on a new converter for the 27" monitors, but don't know if they have since come out with one or not. You may want to check their site.
Or,
get a video card that has a mdp output.
