Put a few drops of penetrating oil or lube around stopper then clamp stopper in wood jaw vise and grab bottle firmly and try wiggling it out by twisting/pulling bottle.
I don't think I'd put it in a vise. Use your hands only or something soft rubber. A vice has no give, so the bottle would give. Your hands are cushioned, so it's like pressing a pillow against an egg rather than a wooden board against an egg. But, yes, penetrating oil ought to work if you let it sit a few minutes!