There are fewer than 10 known, maybe a few more that we are unaware of, but no two are really alike, with the exception of the osnaburg lining, the tarcloth brim as pictured and English Army Cloth (wool). My avatar is of an RD artillery kepi from the Richmond Howitzers, in my collection.
This is probably asking a lot, but would you be able to take measurements off of it?
There are detailed dimensions of an original "Richmond" kepi with a diagram of its construction (similar to the description given previously above; pasteboard visor covered with painted cotton, etc.) in Michael R. Thomas' "A Confederate Sketchbook." (1981).
I would recommend the sources given by @RedRover and if there are additional questions, I would be happy to assist. Getting a true pattern would be the most beneficial, keep in mind that the front dimension, from brim to crown is fairly low. The dimension is most likely a material savings feature, most ACW kepis have a fairly high front dimension 2-1/2 to 3".
For the visor, perhaps you can get pasteboard from art supply stores online (or perhaps make your own by laminating manila paper with glue). Then cover with plain weave cotton, and paint black. Then glue on the edging (also painted fabric), and stitch tightly... looks like perhaps a common leather type stitch (two needles on one thread...). Here is a closeup of Pvt. Royall's cap, which is the one described in the "Sketchbook."
I don't know if this will help but I just acquired a kepi Richmond Guard co B belonging to a Captain Randolph Harrison 1st va. Infantry I can take measurements of what you need. Let me know. I would assume it would be close in size
Bringing the