[Cue-Ball]

Buy a set of "normal" amber bulbs and spray a *light* coat of silver paint on them. The silver paint will reflect the light coming from the outside of the bulb, so they don't look yellow when they aren't flashing. But it will let the light through when the bulb flashes, and it will show up amber like it should. Some of the guys on one of the BMW forums have done this with good results. I think Testors might even make a transparent silver paint for scale models.