I'm thinking about buying a WH20 and know the topper is key, I found this summation fairly interesting although a little old:
https://creditdotpinball.com/2014/05/22/mods-foiled-again-the-white-water-topper-reproduction/
There is also a thread about Laseriffic working with some others on a modern take on the topper: https://pinside.com/pinball/forum/topic/new-ideas-for-white-water-topper I sure hope they are successful as this appears to be one of the hardest things to reproduce ever.