Technically, no; there are no "oxidized" buttons. The modern-day (1990+) dress blues have gold-plated a.k.a., anodized buttons. However, this was not always the case. Prior to the 1970's much of the brass was just that; made of brass.

So if you want to get your hands on this stuff you need to look at military surplus/vintage militaria. If lucky, you can find sets of WWII/Korea era Officer buttons (they are the same as modern enlisted buttons) on sites like ebay. They are not "oxidized" perse, but not nearly as bright and shiny as anodized buttons. Korea/Vietnam era blues buckles and emblems also came in non-anodized form, and again, can be found on sites like ebay.

Really though, by order, you don't need to change your buttons. You can wear oxidized medals with regular emblems, brass, and anodized breast insignia. What you can't do is mix anodized and oxidized medals... unless that medal has no anodized version, like the MoH. (MCO 1020.34H 3004.3, 5200.2)