Lucky escape! I came in here too late to give misguided advice!
I carry a specialist bicycle open wrench, 10mm once side, 8mm the other, very short and thin, but forged nonetheless, not that rubbishy punched-out Park Tool thing, for the few nuts and bolts on my bike, and the Rohloff emergency gearchange. This just suits my present toolkit.
However, if you don't need the 10mm capability (careful -- most bikes have 10mm nuts somewhere, mostly in crucial places, or some really silly, unnecessary place, like on the adjustment clips for mudguard stays), a particularly nice 8mm shifter to carry for the Rohloff emergency shift, because there is no possibility of slipping but it doesn't weigh as much as a ring spanner, is the 8mm socket with fixed male 1/4 inch hex drive in this kit:
http://www.chainreactioncycles.com/Models.aspx?ModelID=10197 It is a good kit, by itself, and very flexible, in that you can exchange one of the bits for a T20 you buy separately, but a bit heavy. So I just used to use the 8mm socket from it with this (it isn't a toy, it is a serious tool; mine has taken years of abuse and is on its fourth bike now):
http://www.chainreactioncycles.com/Models.aspx?ModelID=2926Hobbes