The turn signal on the fender...

[monsta]

Is the only place to get one at Mazda? My driver's side doesn't work anymore.

Thought these were LED??

 

[dima_rus]

they are not LED, that's an OEM solid piece.
You have two options here:

1. Get direct replacement at Mazda dealer

2. Buy a new set of LED ones for Mazda 3 on ebay (what I did)

 

[Heat]

Is the only place to get one at Mazda? My driver's side doesn't work anymore.

Thought these were LED??

Some are, some aren't, depends on the year and trim level. Is it complete dead, or is one of the bulbs burnt out? If all of the lights are out I'd take it to the dealer because there is a bad wire somewhere. If just one of the bulbs are out, well, replace it.