I have LED switchbacks from eBay. I don't want to upstage the vendors on here but I got them for a better price and they are very good quality I can send you the link if you like.
Check out my turn signals here:
Definitely bright enough during the day and extremely bright at night. Check out my lighting video below to see them blinking normally and the brightness at night after installing a $10 relay from Diode Dynamics.