My favorite instrument is a cedar body Spanish classical guitar, but unfortunately, when traveling across country, it got a bit to much sunlight and started to warp around the bridge. So, I removed all the strings and humidified the body, which worked, but took almost a month to get it back to shape. When it came to restringing it, I realized that I had lost the nut in the process. Well, that wasn't to big a deal so I did a bit of calling around and found that none of the music stores, in my area carried one large enough to fit the neck of a classical. That's when I decided I would make one myself. Having a dog that loves bones, it seemed like the logical choice of materials and so I proceeded to get to work, commandeering one of her horde, and planned on how to make a replacement nut.
I suppose this process can be adapted, pretty easily to creating a custom nut for your guitar leaving your stock nut unmodified. I created this one out of bone but there's a plethora of materials you can use such as ebony, horn etc.
Here's the thing with dogs. They leave bones everywhere and only want them when you do so I had to play this one a little close to the chest when 'acquiring' mine, otherwise the sad looks, I'd receive for the rest of the night, would have given me cavities.
**important** If you choose to use bone as your nut making material, make sure they're raw and not cooked. I feed my dog raw frozen bones and never give her cooked as it makes them brittle and subject to splinters. I'd recommend not using a cooked one for the same reason.