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.
My sushi journey started with a similar item from Costco, however not frozen.
Growing up we were forced to take fish liver oil, and any time I tasted sushi all I could taste was fish oil. But the CA rolls from Costco did not have that fish oil taste. After eating it for years I was able move onto better sushi.