Pete,
Oracal makes a Translucent Calend. Product in white for you to cut and apply.
If you call your FELLERS rep they can help you get a piece of it to play with. Since it is translucent you can have a hint of the etched glass showing through the Oracal 8400 Translucent Vinyl. This way you could keep it in house. Also Regal Plastics I know sells Oracal Vinyl by the foot if it is a small job. Feller's may do the same.
Another option is to use an adhesive frosty backlit. The Frosty portion of the backlit will have the same effect as the Oracal 8400 and the cost per square foot is lower as well. Similar effect though. The frosty portion of the backlit picks up the hint of the etched glass. As high as the etched glass is, to print solid white on it could take away from the original substrate (although it does give a bit of a 3D effect like that). You may even be able to print the rest of the text on the backlit for an interesting effect. You probably already know but there is backlit for just about every type of printer - Aquous - Dye and Pigmented, Latex, UV Curable, piazo, etc. Be cautious with a backlit that is too thick if you go this route.
Both of the above options are for a cut of white that is not too intricate.
If you go with printed Flatbed Printers definitely go with UV Curable or offset. But then again, you probably already know that.
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