Would Hleb on the left side work? I haven't seen him play much for Barca, they may be willing to sell.
I was just about to suggest that. He played a good game against Espanyol today, and with Iniesta coming back from injury, Henry rediscovering himself and Messi being Messi, sooner or later Hleb will realize he can't start for Barca.
I think he would be a good signing, as he is perfectly capable of playing on the left or on the right, add to that, the fact he's a hard worker that is willing to track back when needed.
I've never seen Valencia play anywhere other than RW.
He has played on the left for Wigan in a few matches this season, with De Ridder being on the right. He didn't do very well on the left though.