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LED throwies consist of only a few inexpensive parts and can be made for ~$1.00 per Throwie. You can reference the parts list below or download the attached spreadsheet for more info on parts, part's numbers, vendors and application notes. Part: 10mm Diffused LED Vendor: HB Electronic Components Average cost: $0.20 avg per LED Notes: Cost reductions for larger quantities. Comes in red, blue, amber, white in both diffused and clear.
If you only intend to make a few of these, or just want to try them out, you can get all the parts you need at Radioshack. However if you plan to make a large quantity, you should buy all your parts in bulk online, as Radioshack would get kinda pricey for more than a few of these. You can go to the original throwie article (http://www.instructables.com/id/LED-Throwies) for info on where to buy the parts. What You Need: -5mm Diffused LED (the original uses 10mm, but these were cheap in an assorted pack at Radioshack, so I got them) -CR2032 3V Button Cell -3/8" x 1/16" Neodymium Disc Magnet -Scotch Tape, or Strapping Tape (Strapping is better, but Scotch works fine) -Double sided tape, or just about any glue -Leftover cardboard from battery package/other packaging Note: The magnets I used were 3/16" diameter (that's all Radioshack had at the time).