I have a pair of tarnished brass rods threaded into the top of my tanks. The tarnish makes it pretty easy to see the wet line. With 300 gallons and a single Lehman, it doesn't move very much from year to year.
I finally got around to making one. Flat black with notches every inch with the 5th one marked. Used old bike handlebar tape to make a pointless grabber. Looks more like a riding crop than a dip stick
For the assistace towboat I used the bottom 3 feet of an old LORAN antenna painted black with carvings where the marks needed to be back into the white fiberglass. The metal ferrule on the bottom is handy as a handle and keeps it from rolling.