Terry: Have been dealing with Juan and Betty at Purses 'n' Things in St. Thomas for years. They are in International Plaza OR might just have moved to Royal Dane Mall (one of the little alley way/courtyards off Main St.). They are lovely people and have wonderful prices on the best leather goods I've seen anywhere. However, I don't remember seeing jackets or coats - that might be because, due to my luggage/purse addiction, I've not been looking for coats.
At any rate, Juan or Betty would be able to steer you to someone who carries coats - they are kind and honest people and I highly recommend them. If you can't find them, just ask around Main St. and I'm sure someone will know where they are downtown.
Don't know of anyone in St. Maarten, but have a good jeweler friend, Sunny Mahtani, at Grand Jewelers and he would steer you in the right direction. Tell him the big blonde from the golf course in Michigan sent you.