After having problems with one of my traditional lens caps, I bought a 77mm magnetic Kase Cap and Inlaid Ring. I like it a lot, but I haven't tried it in the field. @ShipleyNW has the Kase filter system and expressed disappointment in the "holding power of the cap." See https://rfshooters.com/threads/what-photography-related-item-have-you-bought-or-sold-this-week.2548/post-34424
That's good information.
I have priced out caps/rings from Kase, Haida, Urth, Nisi, K&F, PolarPro, Freewell, and...