Try a crowsfoot. The one pictured is a Snap on. Sears sells Craftsman crowsfeet but I've not seen any open stock, just a set @~$80. All the truck brands have them. I believe Grainger carries Proto and maybe Blackhawk. SK used to have these.
Wrench, Metric, Crowfoot, Flare Nut, 18 mm, 6-Point...