[Hampshire] Any grep gurus here?

Hi All.

I need some help with regexes in grep.

I'm trying to search for a pattern along the lines of:

foo(bar

Note that there is no closing bracket.

Like an eejit, I thought a regex of

foo\(.*

would match that - but grep barfs. It tells me

grep: Unmatched ( or \(

...Which I knew. I'm specifically looking for an unmatched \(.

Does anyone know how to make it do what I want? Using grep -F or fgrep is
not an option - this is part of a much bigger set of searches that I can't
disrupt.

Thanks!

Vic.