Stopped by my local Texas Best Buy store today and noticed a employee putting up some Black Series 6-Inch Archives Wave 1 figures ($19.99 each) on the pegs. Next to these Black Series 6-Inch Archive figures was a empty peg with a tag for the shared Exclusive The Black Series 6-Inch General Grievous figure ($29.99 each). I asked the employee if they have received this figure yet and he said it is scheduled to arrive tomorrow, but he checked his system and there was other stores in my area that currently had them in stock.
Also I just searched on BestBuy.com and the shared Exclusive The Black Series 6-Inch General Grievous figure and The Black Series Archive Wave 1 figures (styles may vary) are in stock as well. You can also use the product pages to check and see if your local stores have these in stock by entering your Zip Code.