Hi, even if you find a stopper the correct style, you値l be very lucky if it fits properly as they are hand made and the pegs all different sizes. If you are sold one at distance, I doubt you値l know if it値l fit until you try it, even if the seller carefully measures it. If a stopper痴 peg is too big, you could get it ground to fit but would probably be expensive.
You might find something cheap and suitable at markets/antique fairs - sometimes sellers have a box of loose decanter stoppers that you could try.