After seeing the Rusty Nail LED Night Light I am thinking that Dick Cappels may be the off set name of MacGyver. If you don’t have any CAT-5 wire handy why not use some of the wire out of an old transformer.
“Those who are familiar with some aspects of coil core selection would quickly point out that the eddy currents would be huge since iron has a low resistance compared to ferrite, or air for that matter, and that there would also likely be other types of large losses. The point here is not that you should run out and buy some flooring nails to make LED lamps, but that this circuit was not “designed”, but was thrown together and worked quite readily. If a rusty nail and some telephone wire is enough to light up a white LED, then the inductor is not so critical. So, relax, go buy a ferrite core and get started on your project.”