Sho, greek letter

As a workaround you could use the very similar letter Thorn, which is available with \usepackage[T1]{fontenc} as \th (minuscule) and TH (majuscule).

Alternatively, you can search through symbolsa4.pdf for thorn, there are quite a other packages that provide one or more variants. Maybe you prefer one of those.

\documentclass{article}

\usepackage[T1]{fontenc}
\usepackage{lmodern}

\let\sho\th
\let\Sho\TH

\begin{document}

This is a minuscule: \sho

This is a majuscule: \Sho

\end{document}

Homegrown alternatives

\documentclass{article}
\usepackage{stackengine,graphicx}
\begin{document}
\textsf{\stackengine{0pt}{p}{b}{O}{c}{F}{F}{L}}

\stackengine{1ex}{b}{\scalebox{1}[-1]{b}}{O}{c}{F}{F}{L}
\end{document}

If you don't want a thorn and you are using luatex or xetex, the character is available as U+03F8 (ϸ) in many fonts, I get

\documentclass{article}
\usepackage{fontspec}
\setmainfont{Arial}
\begin{document}

this is a sho: ϸ
\end{document}