What is "sweep back"? Do you mean you want the bars behind the stem? Get a very short stem and rotate it 180 degrees to face the rear (requires the bars to be re-installed in the stem's new direction).
Have you tried a mountain bike and their flat bars? They offer a more erect riding position. I have one I converted to road use.
I also converted another mountain bike to an upright with sprung saddle, and North Roads bars that "sweep back". This is a fully erect riding position which is very comfortable.
Last edited by Bad Lag; 12-07-19 at 07:02 PM.