Where can I get a turn signal switch for Emax sport?

If the problem is that the switch won't stay on in one or both directions, it can be fixed by removing the switch/assembly from the handlebar, and removing the two small screws that small steel cover on the back side of the switch. Carefully remove the cover and behind it you will find a small spring - be careful the spring doesn't fly away. Stretch a few of the coils this spring out to obtain a longer spring length and reinstall.

Alternatively a good hardware store may have a replacement spring that will work - since the problem is that the stock spring is too weak, the replacement should be a bit stiffer than the original one.

The screw holes often strip upon retightening. If this happens, put a drop of super glue in the hole and quickly reinstall the screw.

If you end up needing a new switch assembly try the calling or e-mailing the various Chinese scooter/part dealers found on the web - you need to send a picture - or another switch style might work.

Hope this helps.