Sony RX100 V Wide Angle Options with Red Filter

[Skating101]

I am trying to find a good option to expand the wide angle field of view on my RX100 V in a Sony housing (67mm threads). My budget is approximately US$500.

I have narrowed it down to two options:

1) Using a red filter behind a UWL H100
INON ワイドコンバージョンレンズ UWL-H100 28M67 【概要】
I am concerned that this will introduce significant vignetting and zooming in to remove the vignetting will reduce the wide angle effect. I am also not certain that the lens alone will significantly add to the field of view of the camera and the additional dome unit is currently out of my price range.

2) Using a red filter behind Fantasea Bigeye Mark 2 Dome
Fantasea BigEye Lens M67 Mark II - 67mm thread Underwater Wide Angle Dome
Various websites have quoted different potential fields of view using this setup up to apparently a 33% increase in FoV (The Ultimate Guide To Underwater Wet Lenses | Mozaik UW).
Will this dome correct the 24mm wide angle to its above water FoV of 85 degrees? This dome will also have significant vignetting at the wide angle.

Are there any other options that I have missed that meet the requirements?

Any suggestions are appreciated.