Use LEDs. A bit more expensive but longer lasting. For the blinking, get one blinking LED per side (left and right). Wire the other LEDs (non blinking) to that LED and they will all blink. So when you want to signal left, just power up the left bank of LEDs and when you to signal right, power up the right side.

All you have to figure out now is how you're going to mount this in a nice case and how you're going to mount the switch on the handlebar.

It's a fairly easy project for even the beginer electronics hobbyist.