I have not been able to find decent jersey knit bed sheets since my local Bed Bath and Beyond closed down (and it was one of the first locations to go).
I can get some at Walmart or Target, but they are not going to be soft and will not last long. I have tried to order online, but even purchasing from a big name brand, they ended up lower quality and higher price than Walmart.
I have had luck with Home Goods, but their selection is always a bit of a gamble.