The S.A.E size u need is 11/32 . For wrenches and sockets not all that uncommon.but not sure about allen wrenches.

You could combine two 3.5 mm hexes. ;) . (They're needed for Campy Delta brakes, now THAT's a tough one to find. Turns out Lambretta motor scooters use them too)

There's always the --SNAP-ON--truck--them people got anything & everything.
But you must bring your bag of gold with you.

My experience with the Snap-On truck is similar to the ice cream truck. Whenever you want one, you REALLY want it, but it's never there. And whenever one does appear, your mom never gives you any money. ("You" = me, I guess.)

Well, I finally got a 7mm hex wrench, and it fits perfectly. I guess that my local hardware store had misstocked some other size wrench in the bin for 5/16" wrenches.

Thanks, everybody.