So, I'm working on fabricating a riving knife assembly for a later AGS10 and while not really the same thing, given what I've learned I think you would need to do a lot of work to get something working (as opposed to just a simple splitter which is what it sounds like you have). I believe a member here named Miles did something similar for a BGS 10, but not sure if he documented it here or not.
I think the easiest method (and what Miles did) would be to find someone parting out a later AGS12 and poach the second trunnion and removable arbor assembly (and hopefully the riving knife assembly with it) as one of the key things is having that arbor housing with the milled space for the locating "hub" of the riving knife.... the more complicated option in my view would be to have the one you have milled to accept the later riving knife assembly, but I suspect that might be a bit of a faff.