Some older bikes used 22.2mm drop bars and had smaller clamps on the brake levers to fit the smaller diameter bars. If you can find a set of brake levers with the smaller clamps, you might be able to transfer them to the brifters. A good source for those levers might be a co-op or a low end road bike like a Columbia, that you find used for next to nothing. Another thing to consider is the ergonomics of the shifters when installed on the bars. If the brifters use a thumb paddle like the Sora shifters to downshift, you may not be able to access them on the new bar. Good luck.