Hey Jake, I don't know where to get the nickel over brass Gretsch eyelets but I do know that Precision Drum has the only eyelets that I could find that properly fit the breather hole on my Gretsch Roundbadges and they only came in brass as far as I can tell from their website. I Hope this helps in any way and maybe if the nickel over brass ones are too hard to come by you can use always use these, or possibly someone at Precision Drum can point you in the right direction. Good Luck!!

Here's the link:

http://www.precisiondrum.com/html/body_parts.html#breatherholeeyelets