If you find any, astonish us all and post the source here. Go&Go tools were reasonably common, but I don't think there was ever a second source for their proprietary cutters. And the dominance of pressed carbide inserts has pretty much eliminated the market for serrated HSS and serrated brazed carbide inserts. So that's an example of perfectly usable but obsolete technology. Hopefully, you got that for a song.
I can't see the actual condition of the cutting edges from the forum photos, but I'd recommend sending the entire cutter out for resharpening. It was common practice to sharpen serrated inserts in place on their cutter body to ensure concentricity. If I were doing it (I have a Cincinnatti #2 tool and cutter grinder specifically to support my horizontal mill habit), I would leave the faces alone and simply shorten the inserts to reproduce the original geometry. The serrations are intended to let you extend the inserts as they get sharpened shorter.
If you want a fussy project (not recommending this), you could acquire an appropriate serration cutter and make your own brazed inserts.