If you are looking for a great Father's Day or a gift to make life a little easier, check out the Mopeka monitoring system on Amazon or other websites. It uses sonar to give you accurate fill levels in two tanks. It has a Bluetooth link to your phone and a physical monitor display for the interior of your camper.
We currently have the internal float gauge that works great but they aren't in stores anymore. They were also only on 20 lb tanks and not 30 lb tanks.
Don't waste your money on a screw-on gauge. It either has pressure or it doesn't. There is no way to know if it's 1/2 or 3/4 full because it's the same pressure.