[texhax] a new math symbol?

[Joe Corneli]

% not font-size independent
\newcommand{\openset}{\mathrel{\subset \hspace{-8.35pt} \circ}}
% this is a nasty hack for 12-point
\newcommand{\bigopenset}{\mathrel{\subset \hspace{-9.25pt} \circ}}

Is there a way to get this symbol to work in a font-size-independent way
(without resorting to METAFONT)?

Joe

PS Maybe someone already has this symbol in a font that I dont know about?