Yes, it is listed here on their US site. If it listed there, it is likely that it will be carried at physical Wal Mart locations as well.
http://www.walmart.com/catalog/produ...uct_id=5516015
Also, it should be at Best Buy, although I don't see it listed online. And EB Games should have some copies.
In Canada, it is likely that SHIV will be carried at Wal Mart, Best Buy, and EB Games - and also at Futureshop.
Of course, there will be other stores as well where one could get the game - these are just a few that I can think of.