The drawing you want is the middle one, on that page. If your pickup has five leads, it isn't a Dually, but that's all right. The two green leads are tied together, and used as the single green lead, in the middle picture.
Ground is the volume pot casing. The switch that is shown in that picture is a SPDT switch. Your push/pull probably has a DPDT switch, on top of the pot. (The pot portion is wired normally.) A DPDT switch is like two SPDT switches, side by side. Just use one side, either the left or the right. The switch, in this drawing, is oriented so that the bottom -- where the white AND orange/black wires are -- is right next to the pot's casing. (In other words, the push/pull pot is oriented so that the shaft is pointing towards the floor, and the lugs are facing you.)
They are actually quite easy to find. If the guitar store near you has a decent inventory of guitar parts, you may find one there. If not, you can get them from Allparts or StewMac. You'll want a 250K audio pot with a push/pull DPDT switch.