Hello Kjell,
Ask one of the professional instruments restoration shop. It's not only the front glass which you could easlily use from a parts instrument...
... but you have to remove and reinstall the chrome ring around it and mostly won't be able to do it nicely.
I got half a dozen of my instruments redone at North Hollywood Speedometer at 6111 Lankershim Blvd. North Hollywood, CA 91606 Tel. 818-761-5136 Fax. 818-761-4857.
Was very pleased with them. I am sure they will also redo the front glass only.
Good luck,
Achim
(Magdeburg, Germany)