Hi Nick, how about changing the flasher to a two-lead device? Can you take its ground lead C and connect it to B?
Short of that, I'm sure one of us can think up a two-or-three transistor relaxation oscillator to act as a series flasher.
Also don't discount a premade unit, something like:
I changed out my motorcycle's turn signals to LED, and they would not flash properly with the stock flasher. So I went up to the local car parts store, bought an "electronic flasher" and plugged it in - presto, problem solved.
-- "Abhorred is the day when it's all figured out." MCJ 200402