You can copy the relevant code from mathabx.sty and mathabx.dcl to your document.
\DeclareFontFamily{U}{mathb}{\hyphenchar\font45}
\DeclareFontShape{U}{mathb}{m}{n}{
<5> <6> <7> <8> <9> <10> gen * mathb
<10.95> mathb10 <12> <14.4> <17.28> <20.74> <24.88> mathb12
}{}
\DeclareSymbolFont{mathb}{U}{mathb}{m}{n}
\newcommand\mathbfont{\usefont{U}{mathb}{m}{n}}
\newcount\mayacnta%
\newcount\mayacntc%
%
\def\mayaexpansion{%
\mayacntc=\mayacnta\mathbfont
\ifnum\mayacntc=0 0\else
\rotatebox[origin=c]{-90}{%
\loop\ifnum\mayacntc>5\advance\mayacntc by -5\repeat
\the\mayacntc\mayacntc=\mayacnta
\loop\ifnum\mayacntc>5\advance\mayacntc by -5 5\repeat}%
\fi}%
\def\mayadigit#1{%
\mayacnta=#1\hbox{\mathbfont\mayaexpansion}}%
The definition of \mayaexpansion has been changed accordingly to this answer of Werner to have properly rotated numbers (requires graphicx).
So, using the command \mayadigit{<number>} you can obtain what you want, as with the following MWE
\documentclass{article}
\usepackage{graphicx,MnSymbol}
\DeclareFontFamily{U}{mathb}{\hyphenchar\font45}
\DeclareFontShape{U}{mathb}{m}{n}{
<5> <6> <7> <8> <9> <10> gen * mathb
<10.95> mathb10 <12> <14.4> <17.28> <20.74> <24.88> mathb12
}{}
\DeclareSymbolFont{mathb}{U}{mathb}{m}{n}
\newcommand\mathbfont{\usefont{U}{mathb}{m}{n}}
\newcount\mayacnta%
\newcount\mayacntc%
%
\def\mayaexpansion{%
\mayacntc=\mayacnta\mathbfont
\ifnum\mayacntc=0 0\else
\rotatebox[origin=c]{-90}{%
\loop\ifnum\mayacntc>5\advance\mayacntc by -5\repeat
\the\mayacntc\mayacntc=\mayacnta
\loop\ifnum\mayacntc>5\advance\mayacntc by -5 5\repeat}%
\fi}%
\def\mayadigit#1{%
\mayacnta=#1\hbox{\mathbfont\mayaexpansion}}%
\begin{document}
$\mayadigit{0}\quad\mayadigit{9}\quad\mayadigit{19}$
\end{document}
which yields

EDIT
I'm not really an expert in Maya numerals...
Try substituting the above code with this one to obtain numbers>20:
\DeclareFontFamily{U}{mathb}{\hyphenchar\font45}
\DeclareFontShape{U}{mathb}{m}{n}{
<5> <6> <7> <8> <9> <10> gen * mathb
<10.95> mathb10 <12> <14.4> <17.28> <20.74> <24.88> mathb12
}{}
\DeclareSymbolFont{mathb}{U}{mathb}{m}{n}
\newcommand\mathbfont{\usefont{U}{mathb}{m}{n}}
\newcount\mayacnter%
\newcount\mayacnta%
\newcount\mayacntb%
\newcount\mayacntc%
\newdimen\mayawidth%
%
\def\mayaexpansion{%
\mayacntc=\mayacnta\mathbfont
\ifnum\mayacntc=0 0\else
\rotatebox[origin=c]{-90}{%
\loop\ifnum\mayacntc>5\advance\mayacntc by -5\repeat
\the\mayacntc\mayacntc=\mayacnta
\loop\ifnum\mayacntc>5\advance\mayacntc by -5 5\repeat}%
\fi}%
\def\mayarecurse{{%
\mayacnta=\mayacnter \divide\mayacnter by 20
\ifnum\mayacnter>0\mayarecurse\fi
\mayacntb=\mayacnter
\multiply\mayacntb by-20
\advance\mayacnta by\mayacntb
\hbox to\mayawidth{\hss\mayaexpansion\hss}}}%
%
\def\maya#1{%
\mayacnter=#1
\setbox0\hbox{\mathbfont 0}%
\mayawidth=\wd0
\left.
\vcenter{\mayarecurse}
\right.}%
\def\mayadigit#1{%
\mayacnta=#1\hbox{\mathbfont\mayaexpansion}}%
and use the command \maya{<number>} instead of \mayadigit{<number>}, as in the following MWE:
\documentclass{article}
\usepackage{graphicx,MnSymbol}
\DeclareFontFamily{U}{mathb}{\hyphenchar\font45}
\DeclareFontShape{U}{mathb}{m}{n}{
<5> <6> <7> <8> <9> <10> gen * mathb
<10.95> mathb10 <12> <14.4> <17.28> <20.74> <24.88> mathb12
}{}
\DeclareSymbolFont{mathb}{U}{mathb}{m}{n}
\newcommand\mathbfont{\usefont{U}{mathb}{m}{n}}
\newcount\mayacnter%
\newcount\mayacnta%
\newcount\mayacntb%
\newcount\mayacntc%
\newdimen\mayawidth%
%
\def\mayaexpansion{%
\mayacntc=\mayacnta\mathbfont
\ifnum\mayacntc=0 0\else
\rotatebox[origin=c]{-90}{%
\loop\ifnum\mayacntc>5\advance\mayacntc by -5\repeat
\the\mayacntc\mayacntc=\mayacnta
\loop\ifnum\mayacntc>5\advance\mayacntc by -5 5\repeat}%
\fi}%
\def\mayarecurse{{%
\mayacnta=\mayacnter \divide\mayacnter by 20
\ifnum\mayacnter>0\mayarecurse\fi
\mayacntb=\mayacnter
\multiply\mayacntb by-20
\advance\mayacnta by\mayacntb
\hbox to\mayawidth{\hss\mayaexpansion\hss}}}%
%
\def\maya#1{%
\mayacnter=#1
\setbox0\hbox{\mathbfont 0}%
\mayawidth=\wd0
\left.
\vcenter{\mayarecurse}
\right.}%
\def\mayadigit#1{%
\mayacnta=#1\hbox{\mathbfont\mayaexpansion}}%
\begin{document}
$\maya{0}\quad\maya{9}\quad\maya{19}\quad\maya{49}$
\end{document}
Result:

19to three bars and four dots (mod and int functions)? The drawing with TikZ is really easy. – Qrrbrbirlbel Dec 02 '13 at 10:20