Apple was stocking the iPhone SE on clearance months back, but it looks like there’s no more inventory. I would check your local retailers, it’s really the only option you have at this point.
Possibly some of the carriers? I tried to get a new iPhone6s and AT&T had them. For whatever reason, they were the same price as an iPhone7 so I got the 7 instead.
I grazed out to my carrier, AT&T, and they do show the SE for sale, but only the 32GB version, for about $350. There is also a free option for a contract period. And no, I’m not shilling for Ma Bell, just trying to be informative.