Below is a simple cutoff circuit which uses thru-hole components, apart from the PMOSFET which is surface mount, but it is a big surface mount, so the circuit should be easy to build.
I haven't included the the decoupling capacitors to keep the schematic simple- you need a 22uF ceramic capacitor, with a 30V, or higher working voltage, and X7R dielectric, +- 10% tolerance or better.The 22uF capacitor should connect neat the PMOSFET source and the corresponding 0V point.
Also get a couple of 100nF capacitors- same specification as the 22uF otherwise.
The funny looking resistor in the gate of the PMOSFET should be mounted directly to the gate terminal of the PMOSFET to ensure frequency stability.