Unlimited Wares through Amazon.com has the Mini Black Batman Dark Knight Twin Blade Batarang Style Pocket Knife for $7. NOW AVAILABLE IN MINI BLUE, RED AND SILVER
http://www.amazon.com/gp/product/B0099UYYD6 - BLACK
http://www.amazon.com/gp/product/B009DR45FC - RED
http://www.amazon.com/gp/product/B009DR3NLE - BLUE
http://www.amazon.com/gp/product/B009DR5R7W - SILVER
This knife is 7.5" overall.
The bigger 11" versions are available here for ~$9, which were also featured in an article through Discovery.com and tweeted by Mythbusters .
http://www.amazon.com/dp/B006017BKA/ - BLACK
http://www.amazon.com/gp/product/B0093LKVYW - BLUE
http://www.amazon.com/gp/product/B006KNUZJW - PINK
http://www.amazon.com/gp/product/B0074FC0X4 - RED
http://www.amazon.com/gp/product/B006KNX8YG - PURPLE
http://www.amazon.com/gp/product/B004FWS74K - SILVER