Just checked Target.com and noticed that their Shared Exclusive Retro Collection 3.75-Inch Darth Vader Prototype Figure is in stock as of 3:08am (Central Time). Price is $12.99 each with a limit of 2 per order. Here is the direct product link.
Update - Still in stock as of 3:25am (Central Time)
Update #2 - Out of stock at 3:35am (Central Time)
You may want to check their site once in a while to see if they pop back in stock.