I have a .450 BPE with a small brass bead that works great in good light but not so much when it gets dim. There's not enough room to do a flip up night sight so I took a piece of mild steel, drilled it out for clearance of the bead, turned it down to the size I wanted, then counter bored the face of the tube so it had a good lip on it. Then I split the tube so it would slide over the sight and have a firm fit. Then I took a piece of Walrus Ivory and turned it down so it fit in the lips of the tube. I glued it in using Super Glue, then shaped the face of the ivory. It just slips over the existing sight and has worked well for me.

I was told years ago the Walrus Ivory was better than elephant because it doesn't yellow. I've also used it dovetailed into ramp sight, for instance a Ruger Blackhawk, my 1911 and they've held up well too.