Bruce L. Bergman writes:

There's one size up that is normally Owned and not Leased, but they
can be harder to get filled. The one place that deals with them a lot
is the Thoroughbred exchange system at Lowes and other DIY stores, but
they do charge a lot more for the convenience.

Could this be a local thing where you are? the only tank exchange I've
ever seen at my Lowes was propane....
--
As we enjoy great advantages from the inventions of others, we should
be glad of an opportunity to serve others by any invention of ours;
and this we should do freely and generously. (Benjamin Franklin)