I used a bruteforce search method with this script:

#!/bin/bash
# options
NUM_DEVS=2

# initialize an Array
DEV=(/dev/ttyACM0,/dev/ttyACM1);
 
## Script Begin ##
 COUNTER=0
 FOUND=0
 echo -e "Searching for devices...please wait\t"
 while (( 1 )); do
          if [ -c /dev/ttyACM$COUNTER ]; then
                  DEV[$FOUND]="/dev/ttyACM$COUNTER";
                  (( FOUND++ ))
          fi
          if (( $FOUND >= $NUM_DEVS )); then
                  break
          fi
          ((COUNTER++))
          sleep .5
# Change Counter value check based on number of devices
          if (( $COUNTER >=10 )); then
                  echo -e "Found only $FOUND devices out of $NUM_DEVS...Please check USB connections & devices.\n\nExiting...\n"
                  exit 1
          fi
  done
 
  echo -e "Found devices ${DEV[0]}, ${DEV[1]}\n"
### End bash script

HTH...