Back in ‘88 I wanted a tinted lens. I tried window tint a couple times to have it bubble from the heat of the dash.
I cut (don’t remember how) the lens out past the opening and silicone sealed a piece of tinted plexiglass in its place.
It looks blacked out when off, but the digits are easy to see when you start the car. It was tricky to drill the hole for the trip odometer reset button.
Using a piece of clear plexiglass may be an option if you don’t find a replacement lens. Maybe the tinted version is interesting.
All I could find at the time was 1/4” thick. I’ve recently used 1/8” lexan to make new lenses for some decorative pole lights behind City Hall (I’m the City Electrician).