I posted the link a few posts back, to a genuine Toyota part. Even if you just search the part number I posted before that it will get you to a supplier.
As for fitting, if you look at the upper part of the clutch pedal,near the spring, there's a little bump stop screwed into the metal frame. This limits the return travel of the clutch pedal. Simply remove this (14mm spanner I think) and replace it with the switch. Be sure to adjust to the same length as the bump stop. Then plug in the cable that's already there, (taped to the bulkhead a bit further up, just needs some searching)