Probably find something in the kitchen that would work....
I've just tried a small aluminium vice from the shed and an aluminium tray (from the kitchen funnily enough ) the vice added another 5 - 10 yards, the tray not so much. I had a few funny looks from the neighbours every time I waved back at Mrs LEDave to say an LED had blinked as I walked up the street.

I'm sure the distance can be boosted with some more tweaking.

Dave