Create own math symbol

Question

i need some additional math symbols in latex. I did draw them in eps and include them with:

\newcommand*\triangleLeft{\ensuremath{\includegraphics{../triangleLeft}}}
\newcommand*\triangleRight{\ensuremath{\includegraphics{../triangleRight}}}
\newcommand*\triangleProp{\ensuremath{\includegraphics{../triangleProp}}}

This works fine for the most things. But it does not work for captions and notes (package: todonotes).

Do you have any better idea? Here is a screenshot of my symbols:

The x is subscript and does not belong to the symbol.

Kind regards, Max

Update:

\documentclass[12pt]{article}%, border=2pt]{standalone}

\usepackage{graphics}

\usepackage{MnSymbol}
\usepackage{sansmath}
\usepackage{stackengine, amsfonts} %


% Non of these work... :()
%\newcommand{\triangleLeft}{\ensuremath{\includegraphics{triangleLeft}}}
%\newcommand{\triangleLeft}{\mathrel{\text{\includegraphics{triangleLeft}}}}
%\newcommand{\triangleLeft}{\mathord{\stackMath\stackinset{c}{0pt}{c}{-0.3ex}{\scriptstyle\leftharpoonup}{\largetriangleup}}}

\begin{document}

\sansmath
 $ \triangleLeft_{\!x}$

$\triangleLeft_{\!x}$

\begin{figure}

% Next line fails!
\caption{$\triangleLeft_{\!x}$}

\end{figure}
\end{document} 

The error is either (for the first two definitions):

! Argument of \@caption has an extra }.
<inserted text> 
                \par 
l.25 \caption{$\triangleLeft_{\!x}$}

or

! Undefined control sequence.
\stackinset #1#2#3#4#5#6->\def \conditioned@inset 
                                                  {\stack@delim #5\stack@del...
l.25 \caption{$\triangleLeft_{\!x}$}

for the third version.

Answer 1

You can obtain these symbols very simply with Mnsymbol and the stackinset command from stackengine:

\documentclass[12pt]{article}%, border=2pt]{standalone}
\usepackage{MnSymbol}
\usepackage{sansmath}
\usepackage{stackengine, amsfonts} %
\newcommand{\leftharpoontriangle}{\mathord{\stackMath\stackinset{c}{0pt}{c}{-0.3ex}{\scriptstyle\leftharpoonup}{\largetriangleup}}}
\newcommand{\rightharpoontriangle}{\mathord{\stackMath\stackinset{c}{0pt}{c}{-0.3ex}{\scriptstyle\rightharpoonup}{\largetriangleup}}}

\begin{document}

\sansmath
 $ \rightharpoontriangle_{\!x}$

$\leftharpoontriangle_{\!x}$

 \end{document}