A typical aero brake levers would still have the cable exiting the hood upward (as oriented on your handlebars). It might be possible to cut away some metal so that the cable could exit out of the bottom of the hood (i.e. in the same direction of the lever along your handlebars).

I messed around with flop-n-chop handlebars and a road brake lever, but couldn't get it the way I wanted (probably because the parts weren't designed to be used that way). I eventually got a set of real bullhorns and a TT lever, which has worked much better.

If you're stuck on steel, they're available. Here's a nice, but relatively pricey, Nitto: http://www.amazon.com/Nitto-RB-018-B...4781015&sr=8-1