If you are talking about the hammer shrouds for the D frames snubbies, Google Waller and Son. Some one new took over the company several years ago. I had bought one from Mr. Waller before he sold the company. The new owner was very nice and easy to work with. They are very high quality, and outside of being a bit off in color and with no rampant colt logo, they are just like the originals. I do not know if he has the screws, but I am sure that Brownells can fix you up with those. I have heard they were flathead screws, but the one I saw, NIB, had oval head screws. I sold my project gun before installing the shroud, but "dry" fitting was as good as a genuine Colt in fit.
The type of screws needed are fillister screws. I can't remember the size used for Colt frames and shrouds. I will try to find that info for you.
I am pretty sure the Waller shroud uses a slightly larger screw, so if you have a Colt factory hammer shroud and a D frame Colt already tapped for a Colt shroud you may not be able to use the Waller screws.