There is at least one alternative.
Often Costco etc. will have 5 gallon tanks with a REAL float based level indicator. That's what I use on my BBQ tanks. Tanks are still reasonable priced. Float moves a magnet up and down to move the level indicator. I've used them for years and they are pretty accurate. So for your 5 gallon tanks it is a pretty viable and affordable option.
For those with bigger tanks, well those gauges are available for other tanks as well. that's the good news. Now for the bad news. I checked with my local propane supplier. They are a unit that replaces the existing valve/float etc. Cost is about $75 for a 30lb tank. And I haven't seen any 30lb tanks being advertized/sold with the float based gauge.
His comment is, they haven't sold any, but they must be a "loss leader" on 5 gallon tank sales.