i was just looking at these last night

http://www.ebay.com/itm/Plastic-Bicy...item53e66cda64

it's not a fully formed idea since i'm just reading the question and like i said just saw these.

maybe find a couple of mountain bike bar ends and mount them as close to the stem as possible, so you'd only give up a few inches of hand space on each side. mount them sticking out forward and there'd be room for one of these on each one. if you have some bar ends around already, a couple bucks for these is a cheap test. if it works, you could extend the bar ends somehow (weld/clamp on some straight sections of handlebar or similar dia tubing), then you could add as many to each as you feel comfortable with carrying.