Yeah. I had a feeling a might be wrond about that and posed ti to some other more knowledgable folk than me. Here is the Readers Digest version of one reply I got:
A multiplication sign is NOT an ex. Unlike using a miniscule "x" from a sans font, a properly designed multiplication sign will look good with the rest of your font.
The alt code (Windows method of inserting symbols that are not on the keyboard) is alt+215 as aikodude said.
It is very possible that a poorly developed font -- or a a "pi font" composed of symbols -- wouldn't have that sign, but you shouldn't be setting anything important in such a poorly designed font.