best disc brakes for sbp

The factory SBP 4" rotor is available from a bunch of sources and is being manufactured by Centric.

Do a search through this forum for factory SBP rotors - you will find the sources, and a lot of availability.

Also, do NOT expect your local auto parts vendor to find the factory rotor, unless you are dealing with a parts man that knows his stuff, and has dealt with Mopars for a long time.