If you don't want to buy a coin door, or would prefer your cab accept any type of coin with no hassles, you can get a few bucks worth of electronics and have any number of coin inputs you want, minimal wiring too.
Make slots in the piece of wood you want your coins to go into. Put an LED on one side of each slot, and a phototransistor on the other side. For the phototransistors, wire the 'collector' sides to 5v. Wire a 1 Kohm resistor to the 'emitter' side, and the other side of the 1kohm resistor to ground. Ignore the 'base' pin, or chop it off entirely. Then put another wire from the 'emitter' side to your ipac's coin input, and you have a generic coin acceptor. If that makes no sense, I'll make a diagram.
Total wire connections for two slots: 12. As a bonus, your LEDs shine through your coin slots a little bit.
If you don't feel electrically inclined, you can manufacture a coin chute out of wood, cardboard, or scrap plexiglass, and mount a microswitch with a lever arm that triggers when the coin drops through. That's how actual coin mechs do it, except they sort quarters from non-quarters first.