I wrote this up in Gameroom Magazine ages ago but you can replace the graphite donuts with a brass ring. Here's the thumbnail summary:
Donut composite (resized).jpg
I drilled out some brass knurled nuts and soldered them in to the steel wire holder in place of the graphine donuts. The brass is still softer than the steel post so it shouldn't wear it down. It worked like a champ while I had the game anyway. You could probably make something out of brass sheet stock too. It wouldn't snap into place like the knurled nuts, but it should work just fine once soldered in.

/Mark