Upvote:4
This does not seem to be a difficult task.
Two quick searches say that you can go from Lagos, Nigeria to Nassau Bahamas on Royal Air Maroc followed by Air Canada with one stop in Casablanca and one stop in Montreal.
Expedia can find all the flights for you but you need to search for Lagos to Montreal and then Montreal to Nassau. Otherwise, it gives you results passing through the US since these are more direct routes. You can also book each leg of the trip the respective sites of each airline.
Should you want to use a travel agent: Do the search yourself on each site for various dates. When you find availability, note the airline, flight number and time. Then call an agent and give them all the details. They should be able to issue the tickets for you.