That sort of thing is actually a favorite theme of my own stories and I never seem to get tired of writing about abused Moms. I don't have anything of the sort posted on BDSM but have a few on RPP. None of them are Mom dominated by Son but Mom getting raped and humiliated while Sonny has to watch and then participate. Some stories with the whole family being put through their paces by rapists. Great fun.
Oh Wait. I do have something on here. See "The Collectors" by Coyote.
I've been contemplating a story of Son domination of his Mom and will get to it soon hopefully. Nothing more exquisite or more absolutely humiliating for Mom than to be stripped, spanked and abused in all ways by Sonny, particularly if he invites his school friends home to enjoy the festivities and "get a little nookie" from Mom themselves.
if you choose you can mail me at:
lennotes@megatropic.com and I'll get some stories out to you that aren't on BDSM.