Look at Jack First and Gun Parts Company web Sites. K and N Frame sideplate screws are the same so don't be too picky and only look under Model 29. Nickle could be a problem, you might need to settle for Stainless Steel screws and polish the heads. Look at both plate/sideplate and yoke screws.You may have to settle for blued screws too, that's all I find.
If you don't find anything on Jack First's site then call them and ask! Google them for the phone number.
Don't waste your time looking. Just take blued screw, strip the bluing and high polish it - works so well no one would be the wiser. I've done this and Flitz polish and a Dremel felt wheel are the way to go.