look in an asian market, or if you're in an area with a good sized asian community, regular supermarkets may carry it in the ethnic sections. i've seen several brands of eel bbq sauce, from very thin and soy sauce like, to thicker sweeter versions for sale. sorry, i don't remember the brand names.
in nomine patri, et fili, et spiritus sancti.
Meh nom eh noh...doot dooooo do do do.