Well one of my sidemarker lights went out. since they are not replaceable I decided to open one up and to my surprise the bulb is replaceable from the inside. The hard part is to separate the lens. Warning the lens is super fragile so don't do this to your good sidemarker unless you're willing to take the risk😉.
My 2015 didn't come with side markers at all. I just bought some led ones from eBay. They're bright, were plug and play and haven't had any issues at all for over a year.