Best Buy is selling a physical CD version of "Bang Bang" with a live version of "Letterbomb" as a b-side. It's available for $1.99 at BestBuy.com and being released September 23rd.
They're including a coupon to get $2 off the full album, "Revolution Radio", at its release in October. As far as we know, the CD release of "Bang Bang" might be a Best Buy exclusive, we haven't seen any other stores offering it.
Not sure yet what live version of "Letterbomb" it includes.
Check out the CD over at BestBuy.com.
If for some reason you can't buy it at Best Buy, of course, someone on eBay is already offering it with a $4 mark-up.
Thanks to Koal Koalson for posting this on our forum.