Berryman's is pretty much the same stuff. I have used it to decarbonize pistons.
It's amazing.
Original B-12 Chemtool is available almost everywhere.
B-12 CHEMTOOL® CARBURETOR CLEANER / POUR IN Cleans petroleum residue and disperses moisture from fuel system, fuel injector, valves, rings, pistons, oil returns, lifters, PCV valve, and oil pump screen with High Energy Solvent Technology (H.E.S.T.). Regular use ensures higher compression, fewer repairs, lower operation costs and increased spark plug and injector life.
Sizes Available:
Part #0101 NET 1 Gallon Can Part #0105 NET 5 Gallon Can
Part #0116 NET 15 fl. oz. Pour Can Part #0155 NET 55 Gallon Drum
Part #0216 NET 16 fl. oz. Squirt Can
Just pour it in the crankcase and run the for 10 mins before your oil change.