I am going on a Caribbean Cruise this spring and have a list of shops on the islands I will be visiting. St Maarten has A Stitch at a Time on the Dutch side and Danielle & Diffusions and Tissus & Harmony on the French side. Castries, St Lucia has Caribelle Batik that makes batik but mostly sells clothing made from the fabric. The organizers are asking them to bring fabric from their other location on a different island for us to be able to purchase. Bridgetown, Barbados has Abed's Fabric World and Flame Shop. Fort-de-France, Martinique sells madres fabric at shops throughout the island.
I hope this helps others in the future.