Lots of ADs at Nathan Road, from Tsim Shia Tsui to Mongkok, Millgaus no problemo. Ask for discount(they'll surely give), if you have the luxury of time compare dicounts from AD to AD. Get a card from AD sales rep you visit, let them write the dicounted amount and show the least to another AD rep. I'm sure you'll get a bargain.
This is what I did, and got US$200 savings. . .