Hi Ben,
I had a regular off the shelf starter button with a rubber cover. I think it was a Narva brand. It looked good initially after I'd polished up the metal surround but it dulled very quickly (
zinc I think).
I was looking at my Milling machine and the switch gear I used when I re wired it. They are industrial push button switches and have a nice feel to them. The button pad is about 24mm in diameter and has a shroud around it so you don't inadvertently press it when you bump it. They are a modular switch which has a backing mount and button part that clip together and the contacter part clips onto the back of it.
I bought it from Midendorps for about $26. They have a variety of colours for the button and even have iluminated ones.
I've got it wired in through a relay so it won't turn over unless the ignition key is in the run position. The original start position on the key still works as well.
Cheers