Small case for mac book air that will hold charger and mouse?
The Booq bags generally have tolerances that are too tight. My iPad with the Apple case didn't fit in their messenger bag that was made for it.

Since you didn't set a price I would suggest the City Slicker case from sfbags.com. I would have bought this bag, but I already had a case for my MBA. I have the version of this case made for the PS Vita and it is an excellent case. There is plenty of room for earbuds, charger, games and extra memory cards. I'm sure there would be enough room in the MBA version of the case for a charger and cables, and by the pictures probably even the DVD drive if you tote that around.