fuel pump O-ring what size, where to get one

[azazel19]

Ok guys i finally ordered a new fuel pump for my lanos. It's been out of comission for several months just needed some cabbage for a 200 plus dollar pump. I have changed the sending unit a few years back so I know the deal I should need a new o-ring where the pump flange meets the tank. Went to a gm dealer and they told me 23 dollars due to shipping costs. I paid like 3 dollars for the last one I got. Can't find the original one just need some dimensions to look at local auto parts stores or maybe a part number for an equivalent from a supplier. thanx