Are you only looking for such online stores as Walmart or Rakuten?
Since recently, I discovered some applications where you can also get some rewards while shopping online stores, just like Lolli(
https://www.lolli.com/). You may also try Fold(
https://foldapp.com/), where you will also get a Bitcoin cashback when you shop and use their platform.
I just saw these platforms on Twitter before, haven't tried yet but I think these are really good platforms to use if you want some Bitcoin rewards/cashback.