I bought my wife a $2k cyclocross bike and she hardly rides it so we got a cheap $100 mountain bike from Target and it turns out the handlebar style is what has been deterring her from riding the cross bike.

So basically I'd like to know if there were flat bar index shifters that would be compatible with SRAM Rival derailleurs. We also have a 105 groupset we could try.

Is this possible or are we doomed to buying a whole new groupset?