According to the comments/caption the tunics are from someone known as "Christo" (bricklink/ebay). I don't see anything 'in stock' in either store. Does anyone else know anything about these custom pieces and how to obtain them? They look pretty cool to me.
PS: He's been mentioned on the forum before, but not much info is given.
PPS: The comments on the flickr page note that it's worth contacting Christo with a message at either bricklink or ebay (links above).
PPPS: Christo states the following in the flickr comments:
Hi, this is a great application for the robes. I realy like it. Morgan gave me the flicker address to have a look. We are currently on vacation in Namibia to have a break from all the vuvuzelas at the soccer. Please tell us what colours you are interested and we will make stock. I can be email at email@example.com with any requests
We have a new ebay store custom_brick_and_minifig.