I bought the LED from overseas. Its a website called
http://www.cutter.com.au/products.php?cat=Cree+XM-LThe model is Cree XM-L, T6 Flux E3 5000K. The casing was a fire alarm detector but you can be creative and glue/solder it just about anywhere you want. Lithium ion batteries, you can buy them online. I recommend used b/c its cheaper and they are rechargeable anyway. I'm fortunate enough to get them by the dozens b/c my work place has plenty. When my company recycles them, I take them home, recharge them and use the batteries for these projects.
A little perspective here. Your average 60w light bulb in your living room will generate close to 800 lumens. One of these led's will generate 1000 lumens, if you have 2 its extremely bright for your 8x8 popup. Keep in mind, you need enough power to run its full potential. Example: 2 AA batteries will lighten up your 800 lumen led but that's not enough power for its full potential, you need 4 AA.
If you know how to solder, its a simple project.