You could take a standard Happs push button and cut the plunger and casing down to what you need, then just glue the parts back together. For a one off button I'd be temped to give this a shot in your situation. A cherry microswitch and a cut down button with enough thread for the locking nut to grip would be about 30mm long (under the panel)
I may have to resort to this. I actually just miraculously found a local store that has momentary switches that are short enough and have NO and NC that highly resemble arcade buttons. I'm going to check it out in person and if I like what I see I will try one of those out. Unfortunately they are 24mm and not 30mm like the Seimitsu ones I ordered, however it's not a huge deal!
As for leaf buttons I'd rather avoid using one.
Another quick question: If I get a switch that has all 3: NO, NC and GND, am I able to hook up two seperate functions to the NO and NC parts of it simultaneously, or will they interfere with eachother?
Thanks for all the replies guys!