I wouldn't try it, you would be better off gluing the pieces back on. The bow was tillered as a stiff-handled bow, without those pieces its possible that it will break there in the middle.
You might be able to use superglue, that stuff seeks out cracks and fills them. Be sure and clamp it back tight right after you glue so the bond will be strong as possible. Superglue doesn't work well to fill cracks.
Your other alternative would be to attempt to pop the piece off entirely, sand off the old glue and glue it back on from scratch. You can use an epoxy or a carpenters glue, they each require different surfaces. I would go with a 2-ton epoxy myself, its stronger and is more forgiving of small gaps in the mating surfaces.
Do also consider that these bows are pieces of history. Its great that you are using them, just try and keep them in as close to original condition as you can. Thats just an opinion.
