Can I buy just the locking pin? What is...
Can I buy just the locking pin? What is the diameter of the pin?
The pin or "skewer" as Thule calls it is 9mm... it has been discontinued as a spare part from Thule but you might be able to find it on the net or elseware, heres the Thule part # (9mm Skewer 8535276)
etrailer has a few replacment locking skewers.