If you're in the market for brass pins, go to your neighborhood hardware store and get a pack of brass escutcheon pins -- they will likely be near the linoleum nails and brads. They're 1.6 mm in diameter and usually come in different lengths, starting with 5/8. They will work perfectly and save you from having to peen both ends as you would have to do if using brass rod. Chances are, though, that you'll just have to look for them on your own at the hardware store because a lot of sales clerks won't know what an escutcheon pin is.
1 pack will be enough to last many, many years. I picked up a pack that will last me for a lifetime for $3.29.