Mmhmmm.
If you're going to set it in any kind of setting beneath the lacquer of the cue, I would strongly recommend against the following metals:
1) White Gold -- will more than likely turn yellow with time, albeit slowly. This happens to -all- white gold, no matter really what anyone tells you. This is because white gold is really yellow gold that has been alloyed and treated to appear temporarily white. This is why jewelers suggest you have any white gold rings rhodium plated every 4 or so years.
2) Sterling Silver -- may tarnish and turn blackish with time... not sure about this if the clearcoat was 100% airtight, though, might not happen.
I would recommend:
1) Platinum -- expensive-ish, but not bad since you only need a little. Will never tarnish or yellow with time. The only drawback to platinum is that it takes on a brushed look with time, which would be nearly eliminated if it had nothing to brush up against under a clearcoat.
2) Palladium -- same metal group as platinum, same properties, cheaper. But harder to find.
In fact, you could most likely purchase blank earring settings and modify them by eliminating the posts on the back to make nearly the exact setting you would need. Go to a local INDEPENDENT jeweler and ask if they have a catalog from a company called Stuller. They're well priced, simple, and very quick to order from. And if they try to gouge you on price, tell them you know the book is listed at triple key (3x cost) and they should do the right thing and charge you 2.2x.
Take care,
-Matt