the only thing i can think of is have it overflow all the way around or just use a little section of cooked sugar to be the 'glass' -- or what about some kind of gelatin concoction -- and use a cake pan for the mold or a pot that's all so nicely rounded inside --

think about cooking some sugar and leaving it in the pot to cool -- reheat it for a few to pop it out and you're there -- so if you just pour some out as it cools you got it -- see what i mean

or a bowl -- i have a couple stainless steel bowls would be perfect

using the 'little section' i mean if the champagne was overflowing with the glass tipped over some -- you only need to have a small portion of the glass to be see through -- the rest would be champagne --

and the 'pouring some out' part -- then the sugar left in the bowl or pot would be hollow -- like how you make chocolate shells for bonbons -- fill mold with chocolate then pour it out so it becomes hollow repeat as necessary for strength then fill --

Thanks for your help.

I did think of doing it that way and looked a every pan, bowl, cake tin that I own and even contemplated using a large bottle!! but a champagne glass is such a specific shape it's difficult to fine something similar.

I'd just make it out of cake, cover it with fondant and not worry about it looking transparent. Use corn syrup or non-stick vegetable oil spray to make it look shiny and paint the fondant to look like there's a colored champagne in the glass. Otherwise you'll be messing with a large amount of sugar/isomalt that will be guaranteed to break on you!