Yes, the circuit that is capable of limiting current flow to a pre-determined 20 Amperes is a current controlled buck switching regulator.
It is doubtful that any kits are available for this kind of device, but they are quite simple and can readily be built from scratch.
It is basically a Pulse Width Modulator that can output high current impulses (20 Amperes) followed by a series inductor of suitable size and a free wheeling schottky diode of suitable current handling ability.
Chips are available which contain all the necessary control circuitry such as the TSM108 made by STMicroelectronics.
Search for and download the datasheet. It has the details.