5870 Confusion

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Just looking for a confirmation here..
Everything I've read says that to do a 3x1 eyefinity setup on my 5870 I can hook up 2 cards to DVI and the last must be a Display port (With appriopriot displayport to DVi adaptor)

Here's my question: Since my card only has MiniDisplay port connections (Every port I connect uses ATI's special MiniDisplay to DVI/HDMI),
DO I need to do the whole display port thing or can i just plug in a third mini Display port to DVI dongle?
(And if that will work.. Where the HELL can I get one?)

Hope I"m being clear here,
Thanks in advance