Apparently Latin Modern Roman does not include it. I don't find it in the math symbols, either. I guess I could define a command changing to some other font for it, but I suspect there's a better way and I just didn't look in the right place yet?
Edit:
One possible solution is the following:
\documentclass{article}
\usepackage[math-style=TeX]{unicode-math}
\setmathfont
[ Extension = .otf,
BoldFont = *bold,
]{xits-math}
\begin{document}
$\disin$
\end{document}
But apparently that will change the font for all math environments, which I am a bit hesitant to do.

unicode-mathand that other one does not address it, even the title is out of context, not to mention the tags on it. – Suppboi May 09 '18 at 16:50