The gauges and controls on our boat are also horizontal, and I have wondered about a solution.
I was leaning towards a digital display mounted on the wheel pedestal, but now I am seriously considering ripping out the wheel and switching back to a tiller. A sloped panel would be nice. I am curious what you find.
Do you have a wheel ? Maybe you can find a digital secondary remote mount solution for just the gauges would you need easily accessible ?
Edit:
Doing a quick image search for gauges, I found this company in California.
Maybe they will know where to get an angled panel. They sell various designs
Another option would be to figure out which boats have them, and contact a marina breaker/salvage yard with that info.