You don't need anything special for a flasher, Cateye has decent one called the EL120 Opticube, it;s a headlight/flasher; can run up to 320 hours on flash mode on just 2 AA bats. Nashbar has it on sale for $13 plus 20% off with coupon; see:
http://www.nashbar.com/bikes/Product...2_10000_200399
OR Price Point has a Sette ST-307 Glo front light flasher for just $6; see:
http://www.pricepoint.com/detail/193...ront-Light.htm