I know this is simple, but ....
I want to use the button on the proto shield to toggle pin 2. I would use a pullup but the schematics I see for pullup resistors show the resistor connecting between the switch and ground. There are no taps on the prototyping shield between the button and ground.
How do I get around this?
A resistor that ties the input to ground is a pull-down, not a pull-up.
If you are talking about the Arduino ProtoShield (Proto Shield Rev3 (Uno Size) — Arduino Official Store) that button is connected to the Arduino's RESET. So you can't really use it for general purpose I/O.
You need to put a button somewhere else on the proto area, so you can connect it to Pin 2. It's up to you if you want to use an external Pull-Up (or pull-down). Personally, I would just enable the internal pull-up resistor and avoid the extra component. The only thing to remember is that when using a pull-up that HIGH = unpressed and LOW = pressed.