lens – Best solution for under/over shots with Olympus tg-6

I’m looking for a piece of advice. My main camera is a crop sensor entry level DSLR that I rarely end up taking anywhere unless I’m on holiday because of its chunkiness and weight. So a few months back I thought I need a versatile compact one to always have in my bag, just as I used to in my pre-DSLR (and pre-smartphone) days. What I had back then was an Olympus mju 8000 tough, so naturally I gravitated towards its 2020 counterpart the Olympus tg-6, the key factor being combining portability with underwater and macro features. There was a moment of hesitation between that and the GoPro hero7, but since I felt the go pro is more video than photo oriented and I’m not quite comfortable with its minimalistic menu as opposed to the Olympus one that I was more or less familiar with, I decided in favour of the latter.
Now I’m looking to get it a dome lens for some nice over/under water footage but I’m only finding third party ones that all connect to additional underwater casing. The cost of both amounts to $650+ which is more than the camera itself. I don’t need the casing as I won’t be diving below 15m anytime soon. So the question is, do you know of any alternatives that can be mounted straight onto the body and/or has anyone tried to do this type of shots with the native FCON-T01 Fisheye Converter. There are much cheaper dome cases for the go so I’m starting to second guess my choice.