Pete, there have been MANY threads about brass and bone and whatever nuts (and saddles) on guitars. Do a search first. I suspect Brian re-cut your original plastic nut, rather than make a new one.

The cheapest fix will be a tiny hole drilled with a pillar drill and a tiny pin through it.

I have in the past rebuilt nuts with glues and epoxies (also cheap if DIY but time consuming), but it is not a good way.