Need help finding high pressure volume champagne style bottles.

TLWR: I want 1.5l or possibly 750ml with either 29mm or cork finish in the 7 volume range. Lean towards 1.5l probably 75:25. Can't seem to find them.

Been looking for some of the 7 volume champagne style bottles and can't find any. Found one place in Canada but they won't ship outside of local.

Homebrew probably has 750 ml but they have 26mm cap which I don't want. They don't list pressure rating but shipping weight should put them in the 900g range for 6-7 volume. Worst case scenario I get those but wouldn't be happy.

They also have the 1.5l magnums but don't list the pressure rating and I haven't gotten an answer back as to what it is. Did a reverse image search which lead to a different vendor and they list them as only being 4.5 volume. Shipping weight on homebrew seems to corroborate with that.

I've tried the whole ask a wedding venue things and they either don't want to or already get picked over. Almost all the champagne bottles I've seen are listed as being < 5 volume. Local brew shop doesn't have it in their order catalogs from their vendors. Been looking on-off for over a year.

Oddly I hate every wine I've tried and am slightly indifferent to the lightly carbonated stuff. The absurdly sparkling wines seem to taste delicious. Makes no sense to me but that's why I'd like the high volume bottles.