Changing SRAM Rival brifters to flat bar - which hydraulic brake levers?
any SRAM 11 speed shifter should work, as the cable pull is the same


Sorry, that's not the case. SRAM MTB 11 speed uses 'X-Actuation' pull ratio (3.48mm / shift) whereas road 11 speed uses 'Exact Actuation' (3.1mm / shift). See here for extensive documentation of cable pull rations, sprocket spacing etc.

However, SRAM makes trigger shifters for at least the Force groupset.