Most Asian grocers will have a frozen butterflied cleaned eel if not several different brands. Usually they'll be vaccuum packed. Chicago Food, Mitsuwa, Tensuke, H mart, and the one in the SE corner of the strip mall on broadway just n of Lawrence all have them. I'd just pop into your closest Asian mkt, look in the freezer case, and if you don't find them, ask someone. Good chance any Asian mkt near you will have at least one brand. They usually have bones, I think, but the freshwater ones are so easy to bone - usually a one piece removal process. The saltwater ones can be trickier, IMO.
P.s. although i haven't been back in quite a while, Mitsuwa's eels have usually been located in the freezer cases along the E (?) wall. Go in, turn right, and then turn left after you get to the end (after the produce, and sashimi.) On your right, against the wall, there is a freezer case.
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