A huge mega ultra +1 for the ScRAM levers. Best damn drop bar brake levers mine hands have ever touched so much that I have used them on two bikes and just bought and installed another set for the new Langsterio and would happily spec them on my Co-Motion if Gevenalle would make a shift lever attachment for them.

Yes they do cost money but they are a super comfortable and ergonomic place to put your hands. They are modern whereas most of the other levers (except TRP I guess) are all kind of olde schoole and have that down tube shifter vibe which isn't a bad vibe but the levers just are as comfortable and when that is where I keep my hands most of the time I want comfort.

If you aren't running brakes in the rear, the best solution is to just do it. However if you are deadset on not having the rear brake because some cool kid said no then you can get the Problem Solver Cable Doubler to which you can run two levers into one brake or vice verse:
BR3342 Problem Solvers Cable Doubler 2:1 Two Levers for One Brake. Your local bike shop might either have one in stock or can order you one quite easily if they are a QBP dealer which probably most would be unless they are crazy.