Outers Foul Out System
There are some Outers Foul Out Systems around like on EBAY etc.
There are also some videos on how to make one but
BEWARE of any current going to the barrel etc. higher then .4 dc volts. If you don't have measuring devices and/or are not electrically inclined then IMO don't try and do it.
Most folks that make their own use 12 volt car batteries and a "step" down control with a built in meter in it or a separate meter to get down to .35 dc volts and timer to shut down "the system" like say after 20 minutes. Really don't want to run more then that before checking the rod and cleaning it.
Number of folks use the schumaker battery companion or even a battery charger and step those down. That way you got the battery charger as one when you don't need it stepped down.
Again the rod is positively charged and the barrel negatively.
Chemical solutions for either copper or lead removal are pretty easy to make.
Comes down to if you want bare metal or you want some fused deposits in the grooves.
From what I know Outers quit making them for two reasons. Fair amount of money and folks that don't know or don't agree with the concept of metal fusion in rifle bore and how it cannot be removed with non acidic solutions. Or maybe they did not even care.

Those of us that have one love em those that don't just chalk them up as another gimmick by a manufacturer to get their money.
I don't have any pics so will have to take the following on faith but a few years ago, maybe 15, a doubting Thomas who had access to a company lab had the barrel of one of his .22 rimfire rifles scanned using an electron microscope after he had super cleaned it with a non acidic bore cleaner. The lead still left in the bore surprised him.
noremf(George)