How many do you have to make? If only one, lay out the hole with dykem, drill a hole in the middle and get after it with a file. With enough care, you should be able to do a fine job. Especially if the shaft is available for trial fits as you go.
I'd think you'd need at least two small files: a half round and a traingular. You'd probably want to grind a safety edge on one flat side of each file.