Some items are avail for replacement. They can be ordered by your LBS from QBP/BTI, etc. However, the piece that you are looking for is not avail for purchase.
You either need to purchase a new shifter - which run about $38.00 for a single or around $70-75 for the pair - or find someone who has broken a shifter, but the internals are still good.
You either need to purchase a new shifter - which run about $38.00 for a single or around $70-75 for the pair - or find someone who has broken a shifter, but the internals are still good.