Looking for a good web font with both Arabic and English support
Google just released this, In theory with support for every language This could solve your problem.
Yes, it is one of few examples that I found. Probably the best one. Also: FF Amman Sans (I don't know if it's correct to use), Myriad Pro, PF Din Universal, Shilia ($165 for one font style, $1,320 for all of them)
You might find something useful here. I'd probably look at the ones by Dalton Maag or Linotype first.