You could try SVG Air. They operate a scheduled service from Barbados/St. Vincent as well as charters. We have used their scheduled service in the past and it was convenient and on time.

We returned from St. Vincent via Barbados on Liat earlier this week. Our scheduled non-stop turned into a Caribbean tour with stops in Martinique, St. Lucia, and finally Barbados (with no luggage when we got there). We barely made our flight from Barbados that initially had a 6 hour layover.