Dan,
You can purchase most of the products you are looking for from Mouser Electronics
www.mouser.comWe use Belden wire because of it's reliability. It costs a little bit more but last longer.
The 2 pair wire is Belden # 8723, 2 pr, 22 awg, sheilded.
The 3 pair wire is Belden # 8777, 3 pr, 22 awg, shielded.
I would recomend the three pair wire for the start and finish. System A, B & comm.
The dual banana plugs are Pomona MDP-O which are the black ones. Thay make other colors if you need them. Remember the double banana plugs usually don't fit the start gates, photocells, or headsets so you will need some single ends or jumper cables to go from a double to singles.
You can also find the NEMA Plastic enclosure boxes at this site.
For your dual female binding post I like the ones from Radio Shack Model: 274-718. These will fit the Pomona dual banana plugs but you can also attach bare wires to these because they have screwdown heads.
Hope this helps,