I have quite a few packs of 5 Chrome letter opener kits. You get the Chrome blade and the little knob that butts the blade and handle for a finished look.The blade is 4 1/4" long and the handle is 3/4" long. $12 mailed in the U.S.
I used a caliper to measure the chrome knob that fits flush with the handle and turned a pen blank down. Also used a chuck and supported one end with a live center. After turning and sanding the handle, I cut the end off in the live center and finished by rounding the sawn off end with sandpaper.Drill a small hole in the end and glue the opener handle in.