NewTacho.de ? IIRC their faces aren't transparent, so you'll have less light. Then again.... my experience is that it's this transparency that makes the numbers hard to read at night.
NewTacho.de feature an installation video
Needle removed with two tea spoons. Interesting way to 'lock' the needles in (one) place.
It's possible to replace the glass, but it's difficult. That glue is NOT giving up easily. If you aren't able to find a used 'top', or get tired of looking for it, maybe try to remove the scratches first. There must be a million DIY videos on the web.
SOS Diagnostics do a lot of instrument work. Maybe they have something in a box somewhere?
When you put it back together it's mega critical to seal perfectly. Spend time positioning the sealing gasket correctly in every little corner to avoid leakage. Don't over tighten the screws - they are grabbing into plastic and aren't really meant to be tightened more than once.