Where to buy some long T-Slot studs for the Shaper Origin

To mount a custom jig on the Shaper Origin Workstation I need some longer than normal T-Slot studs. Can anyone suggest where I might buy some 1/4-20 x 4 1/2 inch T-Slot studs either locally or online. The problem is I can find 3 1/2 inch long ones, but nothing loinger.