Gearhead wrote
Why not put a commonly available nut (or otherwise interesting, like Earvana or something) and lock it in place with a wooden spacer on the tuner side?
I think you'll have to go with Gearhead's advice here, never heard of a non locking nut specifically made to fit a locking nuts channel. You could always just use a locking nut and just not use the pads to lock down with, it'll give you a more consistent tone between fretted and non-fretted notes.
