Just found this site desperately seeking the emerald green relish of fame.
Well, I found this site who purports to sell it:
http://www.hometownfavorites.com/shop/candy_cat_js.asp?abc=1&char=B&id=535
$1.60 for a 10 oz jar.
Also, for those of you who haven’t tried it, the other poster is spot on: Weber’s Mustard from NY is awesome mustard.
Cheers!