I think you can get empty Juul pods nowadays, but they're an after market development that you have to buy separately (and you'd want to have to want a Juul I guess.)
IDK too much about the others, I'm not much of a pod person, but I do know that for many pods that come prefilled, you can refill the pods after they're empty using a variety of cunning methods.
I don't know how "convenient" that would be, and I'm going to bet there is probably a pod of such nature, whether it will suit your
vaping style is anyone's guess. But, it's a good idea, I'm going to bet there is one.
Here's a link to a thread that was pretty active on some of the newer pods, it might be helpful.
https://www.e-cigarette-forum.com/threads/pod-mods-which-one-are-you-liking-the-most.760037/page-34
Good luck in your search.
Anna