Is it practical to build a wearable project that draws 9A @ 12V?
Expanding on my comment, The ebay page cites 2.2W consumption, with a  12V supply voltage this corresponds to 200mA per 5 meters. Assuming this is correct, 15 meters of lighting will draw approximately 600mA. A high end rechargable NiMh AA battery is rated at around 3000mAh. With this in mind, a battery pack of 9 AA batteries (12 V) will power the display for at most 5 hours (theoretical limit), but likely closer to 2.5. 

However this is based on several assumptions, primarily that the rated power consumption is true and represents an "always on state", because if the power supply is rated with half or less of the LED's on at the same time it could skew your performance (and drive the supply current way up)

Keep in mind that 600mA at 12V corresponds to 7.2W, so be sure that you use fat enough gauge wire for the return current, and that any resistors are beefy enough to handle the power on individual lines.  

P.S. $80 dollars for 5 meters is excessive, you might be better off rolling your own