I am in the process of desiging a full-size upright Mame cab, and I intend to use coin mechs with tokens.
And you are a little behind on the authenticity if you are running MAME.
True enough, in fact I played a game of Paperboy with a joystick last night, but you can't have everything, right?

Anyway, big news.
I was showing my wife what an ---uvula--- pbj is, and she pointed out to me that I had in fact bought some tokens when I built my bartop!
I had originally planned to build an upright cab, but because the whole project started out as an experiment with a Raspberry Pi, I thought it would be cool to make a small machine instead.
So, I bought these tokens a couple of years ago from a Pachislo place called akimono.com.
When they arrived I was a bit disappointed because they were thinner and lighter than regular .984 tokens.
I honestly thought that I had returned them, but I guess I didn't get around to it, because my wife just pulled out a coffee can full of them (500 tokens) from the closet

They are .984 in diameter, and made of stainless steel. They are a little thinner than a standard .984 token, and because of this, and because they are stainless rather than brass, they are a little lighter.
They aren't as nice as conventional brass tokens, but they'll do for now.
I probably will invest in some Any Coin mechs to use them with.