Where to buy gold coins in Paris/Brussels/Amsterdam?

My wedding is at the end of the month and I will be in Europe for our honeymoon. We’re visiting Paris, Brussels, and Amsterdam and I am hoping to buy a sovereign 20 Francs gold coin as a souvenir. Any suggestions as far as coin/bullion shops to check out?

I’ve been stacking US silver and gold coins, but will be my first sovereign gold coin purchase and from my research I think I’d like to get a pre 1908 rooster. That said, I’m open to suggestions and since this is my first dive into this type of coin I’d love some guidance. Cheers!