$4.27 is way too much.
Take 20 inches or so of a heavy piece of core wire (#22 or so) from a bass string clipping and roll the last two inches of it between two files. This will roughen it up a little. Then swedge it about an inch from the end with a hammer on an anvil, (or heavy vise), until it is just a scant bit too wide to pass through the agraffe. This will create a flattened burnisher/chaser. Cut the end just short enough to that there is approx. 3mm of round wire in front of the flattened portion and chuck it up in a 1/4" drill.
The 20 inch length allow you to insert and guide the wire by hand without worrying about getting the drill perfectly lined up with the bore of the agraffe, and the sledging will create a leading "shoulder" to the swedge that leaves a soft exit in the agraffe hole.
You may need two or three of these, as agraffe holes are rarely the same size, even on the same agraffe. You want to be able to pass the swedge through the agraffe with light pressure from the pushing the drill into it. The roughed edges will begin to show a brass tint as it passes through successive agraffe. It can be done without the roughing if one simply wants to burnish, but I found that a very light abrasion does the job faster.