I got this from Amazon, and the Commando 4G fits perfectly, even with extended battery!
Amazon.com: ARKON XXL-ARMBAND Sports Armband for Samsung Galaxy S3/S2 and 4.3-Inch or 4.5-Inch Screen Smartphones - 1 Pack - Non-Retail Packaging - Black: Cell Phones & Accessories
Amazon.com: ARKON XXL-ARMBAND Sports Armband for Samsung Galaxy S3/S2 and 4.3-Inch or 4.5-Inch Screen Smartphones - 1 Pack - Non-Retail Packaging - Black: Cell Phones & Accessories