What type of ultrasonic transducers are used in medical ultrasound devices?
US transducers use an array of piezo-electric ceramics mechanically tuned to desired frequencies.  You can usually buy what you're looking for, or order custom parts, at places like https://piezotechnologies.com/ 

Note that the handle you're looking at is probably many individual crystals in an array, not a single element.  The US device often sends out a complete wavefront.