At your arcade... and before you think that is a smart ass answer, just let me tell you I have bought most of my cabs from Arcades and spent around $100 or so to haul them off.
You can also try <a href="http://www.superauctions.com" target="_blank">http://www.superauctions.com</a> . They are a traveling auction of arcade goodies, sometimes Neo stuff pops up. Or, depending on your area, you can contact a local distributor, such as Benson or one of the smaller ones in your area (look in the phone book under amusement).
I really recommend getting one locally and not off an online site or auction. It really helps to be able to see it first (just be aware, most arcade stuff is in dire condition and will need to be worked on) and in order to save you buckets of cash in shipping.
-Nick