Here's my light setup. I got the lights at LHS - they were eflite branded, didn't say what they were for.
I just soldered them together, and soldered on a small plug. I use a 30mah cell. The batt weighs 1.2g, the lights weigh 2.1g for a total of 3.3g's. Lights last a while on a charge and are very bright. Ladybird flies well with the extra weight.
I tried tapping in to board's power and they just weren't bright enough.
It's not the neatest job, but it works
I'm also using the 9imod DSM board and my DX8