Are Adafruit RGB 30 LED/m flexi-strips suitable to wear in large numbers?
Edit: Sam caught an error by the OP which changes my answer.

You will need to supply a total of 36 amps if you turn everything on a once. But this might be a bit boring because you will just look like a large white light bulb. Consider adding a small programmable controller that cycles through various colors and turns sections on and off to make it more interesting. This will also greatly reduce the energy that your battery will need to supply.

To help you with your battery calculations, if you had 1/3 of the LEDs turned on at any one time on the average, you would then only need ~12 amps.  Battery life is expressed in amp-hours so a 12 amp-hour battery would power your LEDs for 1 hour. If you used a commonly available 7 Ah battery, this would power them for less than 1/2 hour.

The app notes indicate that the strips will work with 9 volts. If you used a 12 volt battery with a 12 volt to 9 volt buck converter, you could extend your battery life by at least 15%. The LEDs would be slightly dimmer but it may be worth it for the extra life. You could also consider Li Ion cells that add up to a voltage lower than 12 volts.

Do break your LED strings into strips that draw no more than ~4 amps each and put a 5 amp fuse in series with each such strip from the battery to head off a potential clothing fire. Monitor your battery temperature when in use to make sure it is not getting hot. Always charge your battery away from the clothing in a safe fashion.

Have fun with the project.