The MnSymbol package provides it.
\documentclass{article}
\usepackage{MnSymbol}
\begin{document}
So a rational map f: $V_1 \dashedrightarrow V_2$ is not a map at all;
\end{document}

pre length
is already added, therefore the left arrow looks fine, post length
fixes the right arrow head. The following example also centers the arrow around the math axis:
\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{
calc,
decorations.pathmorphing,
shapes,
arrows.meta
}
\newcommand\xlrsquigarrow{%
\mathrel{%
\vcenter{%
\hbox{%
\begin{tikzpicture}
\path[
draw,
>={Implies[]},
<->,
double distance between line centers=1.5pt,
decorate,
decoration={
zigzag,
amplitude=0.7pt,
segment length=3pt,
pre length=4pt,
post length=4pt,
},
]
(0,0) -- (14pt,0);
\end{tikzpicture}%
}%
}%
}%
}
\begin{document}
\[a \xlrsquigarrow b\]
\end{document}

Best Answer
amssymb
has one called\rightsquigarrow
, but you may find that it's not long enough: