A free SVG version can be found on Wikimedia: Symbol thumbs up.
The file Symbols_thumbs_up.svg can be converted with Inkscape to PDF like in this answer:
inkscape --export-pdf=Symbol_thumbs_up.pdf Symbol_thumbs_up.svg
The white margins can be removed by pdfcrop:
pdfcrop Symbol_thumbs_up.pdf
The result is Symbols_thumbs_up-crop.pdf.
In LaTeX it can be included, mirrored and resized by package graphicx with a driver that supports PDF. Otherwise it can be converted to EPS via pdftops of xpdf or poppler:
pdftops -eps Symbols_thumbs_up-crop.pdf Symbols_thumbs_up.eps
LaTeX example that defines \LeftThumbsUp and \RightThumbsUp:
\documentclass{article}
\usepackage{graphicx}
\newcommand*{\RightThumbsUpAux}[1]{%
\begingroup
\sbox0{Ag}%
\raisebox{-\dp0}{%
\includegraphics[{%
height=\dimexpr\dp0+\ht0\relax,
#1%
}]{Symbol_thumbs_up-crop.pdf}%
}%
\endgroup
}
\newcommand*{\RightThumbsUp}{%
\RightThumbsUpAux{}%
}
\newcommand*{\RightThumbsDown}{%
\RightThumbsUpAux{origin=c,angle=180}%
}
\newcommand*{\LeftThumbsUp}{%
\scalebox{-1}[1]{\RightThumbsUp}%
}
\newcommand*{\LeftThumbsDown}{%
\scalebox{-1}[1]{\RightThumbsDown}%
}
\begin{document}
\begin{tabular}{ll}
\LeftThumbsUp & \verb|\LeftThumbsUp|\\
\RightThumbsUp & \verb|\RightThumbsUp|\\
\LeftThumbsDown & \verb|\LeftThumbsDown|\\
\RightThumbsDown & \verb|\RightThumbsDown|
\end{tabular}
\end{document}

:POk, joke aside, you could create or get a vector graphic and use the picture as a symbol, see here: http://tex.stackexchange.com/questions/22487 or here: http://tex.stackexchange.com/questions/31490 – Count Zero Jun 15 '13 at 11:19