I wanted to try out some polymorph and at the same time provide a small light for reading in bed late at night. I whipped one together with a couple of white LEDs, some batteries a small handful of polymorph for the diffuser and a couple of bits of vero board.
Total cost maybe 2 quid... reading in bed whilst the Mrs is sleeping, priceless!
Preferably with an on/off switch
I used white, but whatever colour you want
15g or so of Polymorph
To create a diffuser and hold the LEDs in place
Solder LEDs, resistors etc onto a bit of veroboard. I used a female PCB header for plugging in the battery so that I didn't have to route long cables around the frame. Leave some length on the LED pins so that they stand up a bit from the veroboard
Fix your battery holder to the coathanger. I used sticky tape so I can easily remove it when the batteries go flat