6-channel piezo buffer jfet circuit
Almost all modern opamps are CMOSFET input, which will provide the same picoAmpere input currents that JFETs achieve.
To select an opamp, determine if you need

Rail_to_Rail inputs (such as 0v to +3.3v)

Rail_to_Rail output (often spec'd as &quot;within 0.01v of rail, for 10Kohm load)

unity_gain stable (needed if you only use for Gain = +1) and for 100pF Cload

of adequate slew_rate ( 2 volt peak_peak output at 20,000Hz needs more than 120,000 volts/second , or 0.12 v/microsecond). So pick the default of 0.5v/uS , or faster.