Yes there is a walmart, but only one actual grocery store, and it now stock frozen sushi.
Update: I shared this picture with my local gaming group, one of them went and picked up a tray.
He tossed it into the fridge and tried it this morning.
I had the first piece. It is supposed to be "Refrigerated Only" by the packaging, but honestly, with a fridge thaw, it tastes just fine. I've had plenty worse than that.
If I was not vegetarian I would give it a try. The closest place to get sushi to us is an hour drive.
I don't know the brand, or even where it was bought, but my experience with, like, prepackaged sushi is that it seems to have a stronger flavor, though less refined in a sense. They also seem to have a tendency to put a bit of wasabi in nigiri under the fish. I think also a tendency to have a lot of surimi with strong flavor.
Wouldn't complain about having it though, it's still nice, mostly just ends up feeling kinda samey.
Not sure how that tastes but have heard stories of frying some in mayonnaise.