The brass rivet method looks fine, but as the stock ages, will have to be adjusted, as it will protrude, as the stock shrinks and wears.
The wood chips and glue method is similar to the above in it's wear habits, but less so, and may not take stains well.
The drill it out and put a dowel of the same wood in the hole method, is more visible than the glue method after time, but tends to shrink and wear just like the rest of the stock.
For best effect, use a dowel made from the same wood, same coloration, and cut cross grain, so you can align the grain with the grain of the stock.
It's a trade off, you'll have to pick the method you like best.