I purchased a couple of the Costco 20lb empty bottles with internal float type gauges. They were about $28.00 each, so not too bad cost-wise. The gauges are accurate enough to get a general idea of the fuel level. (similar to a fuel gauge in your car). My old tanks were needing painting
anyway, so it made sense.
The drawback to these tanks and the see through fiberglass ones is you wouldn't want to trade them in at the exchange dealers. I have been caught in that predicament before where there were no re fillers in the area.
As to the comments regarding safe storage of the one pound bottles, I have found them to leak after dis-connecting an appliance. The valves are not designed for durability and can seep. I have experienced this on several occasions where I could hear hissing or could smell the gas leaking from the valve. Most times the leaking bottle could be put back on your garage shelf or in any open air spot and hiss away until the bottle emptied with no bad consequences. If the bottle was in a spot where the gas could collect then ignite it could spell disaster. If you have a leaking valve you can re-attach the bottle to the appliance, turn it on and back off, then remove it and see if it is sealed. Most times it will re-seal by doing that.
I don't go so far as to soap suds test these, just listen up close and use my nose.