I wouldn't try to hide it. Make it something cool looking that follows the natural lines of the missing chunk. My recommendation would be to use inlace resin with some sort of filler....Coffee grounds, pepper, brass shavings, glitter, whatever. Build a masking tape mold that'll leave the material a little big so you can drill/turn it back to flush. I've found that CA doesn't work all that great as a filler for very large gaps or missing chunks. Even if you get it to not be brittle, it won't be perfectly clear in most cases. You might get away with using epoxy but I'd recommend inlace.