Topeak makes what is known as a Tour Leader's handlebar bag, in two configurations, IIRC. I have one for my touring/rando bike. It is narrow enough not to interfere with the brifter shifting, and the bar mount goes either side of the stem, leaving plenty of room for a computer OR it has a removable mini-bar of its own on the mounting hardware that can be used (if you don't use, just toss it).
The bag has reasonable space in the main compartment, a top section for documents, a clear plastic map holder than velcros on, zip-up side pockets, a top carry strap and a shoulder strap, and a decent-sized front pocket. Phew!
I like it, although I have modified it slightly to lower its height on the bars (don't ask -- it's more complicated that it seems).