Cut Steel Buttons?

[MacMillan of Rathdown]

I want to replace the buttons on my PC coatee. The best way I've found to describe what I'm looking for is that I want buttons (and a cantle) with "high lustre", but not "shine."

Then you might want to consider having them silver plated. As Mr. Ripley used to say, Believe It or Not silver plated button and cantles used to be quite common and were not that much more expensive than chrome.

I noticed on the "Military Metalwork" link, that their cut steel buttons are plated with Rhodium to prevent rust so I wonder if that effects their glitter-factor?

Slightly. It gives them a bit more shine, in addition to preventing oxidation. All silver hilts leaving Wilkinson Sword were routinely Rhodium plated for that very reason.

I had been resigned to saving up for Sterling Silver, but I'm wondering if anyone makes cut steel buttons in the traditional diamond shape.

Like JSFMACLJR said, the diamond shape buttons are not a requirement-- I'm sure you could have anything made, at a price!