Um .. thought the point of Soccer shirts was to promote the club's name, colors and sponsors.
What you are asking for is a shirt with no name, no sponsor and colors that are not applicable for a specific club. Right?? Is this to get around the pub rules of no 'team shirts allowed'? So you want ManUnited colors on the top and Arsenal colors on the bottom??
I was in HK and directed 'up north' to a huge couple of streets with lots of vendors (not Stanley Market - on the Kowloon side). Had to take a cab .. lots of knock-off products like shirts and CDs and luggage .. and electronics. Do not recall the name of the area tho... hotel suggested it for Soccer shirts.
I found a LOT of non-traditional teams.. like China and the Phillipines and colors that I had never seen before. Yes 99% were fake but my highschool aged cousins LOVE them. They are tired of the traditional EU teams!
What you really need is to find a knock-off manufacturer that will sell the unfinished shirts to you before they put on the fake logos.