The MaxBotix high resolution, low voltage MB1023 HRLV-MaxSonar-EZ2 is a good compromise between sensitivity and side object rejection.
The MaxBotix low voltage MB1010 LV-MaxSonar-EZ1 offers very short to long-range detection and ranging, in an incredibly small package with ultra low power consumption. The MaxSonar-EZ1 detects objects from 0" to 254".
Ultrasonic Module HC-SR04 Distance Measuring Transducer Sensor.
100 pack of square cable tie mounts with adhesive backing. 3/4 inch.