[dcb]

I think the "constant flasher" might be something to find in the towing section of the store. You might also get lucky by "circuit bending" the existing flasher.

What I did when I switched to LEDs was to open up my flasher, set it up on the bench w/12 volts and an LED blinker "bulb", and took a small electrolytic capacitor and held it in parallel w/capacitors already on the board till I found one that had an effect on the flash rate, then I tried different sized capacitors till I found one that gave a reasonable rate, and soldered it in parallel and closed it up.

Also beware of LEDs with "built in load", some LED makers got tired of explaining why the flashers acted up and started making their LEDs suck up a bunch of current they didn't need. If you put in LEDs and the blink rate is fine, then they might be no more efficient than regular bulbs because of this.