I don't think there are any stock washers, but the underside of the nut is going to be what you'll use to pick one out. Chances are you're going to have to buy a washer with the same inner diameter and grind or file the outside so it fits the hole, or buy a small washer with the right outside diameter and hold it in a vise while drilling the inside bigger.
On the MIM neck, will the nut come out without the little black plastic lining in the hole interfering with it? On a USA neck with biflex, the walnut plug gets in the way as well as the metal plate/gate under the string nut.
"Why don't you just make 10 louder, and make 10 be the top number, and make that a little louder?"