My piddly two cents worth.
I would consider a laser, to see if that would get it done.
I have three guns with fiber optic sights fitted. A Browning Buckmark came stock and I fitted both my Ruger GP100's with them. They work great in very low light conditions. Worth a look.
I have three guns fitted with concave gold beads. They work well in lower light. I had Nelson Ford in Phoenix fit my model 28 with one. He milled off the stock sight, dove tailed a mount and fitted a gold bead to the replacement, which he pinned into place.
I have a 625 as well. Chamfering the cylinder makes the moon clips slip in for a fast reload. I can imagine using clips in the model 21 might be a nice feature.
The model 28 lent itself to my front sight modification, as there was material attune end of the barrel to dovetail into. I tried to do it as part of upgrades to my old model 10. Ford indicated that even with the bull barrel, he couldn't fit a handmade gold bead to it.
Ford can do the work you describe, if it is possible to make the mods. I know there are other excellent Gunsmiths who could as well. If you describe the work you want, he likely could help you. Reach him at *thegunsmith.com*.
My 625 is my most customized gun. Not so much invested as some have with their guns here. Trigger jov, chamfered cylinder, gold bead, sharp edges off trigger and hammer. I have oversize grips from Hogue in Tulipwood on it.
It was worth it. It fits my hands like a glove. I love 1911's, but the .45 ACP begs to be shot in a revolver. I would do it again.