I use the welding supply store here, I think it's the only place in this area to fill tanks. But it is cheap.
Plus I was dropping off my 2 20# tanks and the owner asked what I used them for. I told him, he said he could help and gave me a
tank that's probably 30# and one that's probably 35#, both filled at the 20# price. That's why you look for a local operator.