Finally found one at Napa.  The Home Depot, Lowe's, and Ace all struck out
in person, and CarQuest and Oreilly over the phone.  Did end up getting
some copper washers from Oreilly because when the coolant shot out after I
sheared off the bolt head, it took the washer with it and I haven't been
able to figure out where.

I think the actual length is 12mm.  They didn't have a brass one but I got
a zinc plated one.

Thanks again, everyone, for all your contributions.

mike

On Thu, Dec 13, 2012 at 2:10 PM, Mike B <mbucchino@charter.net> wrote:

> 13mm hex head, 8mmX1.5 threaded, 1/2" (13mm) long will do.  A copper or
> fiber washer under the head for sealing purposes.  Lowes or HD will have
> it.  HF sells a nice assortment of copper washers for a few bucks.
>
>