I wasn't quite sure where the British Virgin Islands, I'm in a state of study-induced fatigue, were until I looked it up on google.com to see if there were any stores around you. Having done that I can see just how unavailable pet stores are, I only see a couple on google maps. There are probably more (feels like I always miss something), but I can't see 'em.
I would still double check to see if there are any feeder insects for reptiles or any of the above suggestions available at your available store but if there is not I think I might have a solution. You could possibly try to find wild insects, make sure they are healthy, and feed them those. If you do have to resort to this, maybe see if you can breed your own feeding stock since this will let you guarantee the health of your fish feed.
Again, I only suggest this as an absolute LAST RESORT because with wild insects you cannot guarantee the health condition that the insect is in, or what nutrients you are giving to your fish via the insect. With wild insects you also lose the ability to guarantee that the feed is not diseased/tainted in some manner. Like I said before, totally a LAST RESORT option for the aforementioned reasons. Definitely check to see if you have any available kind of feed for your fish in local stores before resorting to my suggestion. Maybe ask the store you got them from, if you got them from a store, what they fed them.
Walking on Sunfish, WhooOOOOooo. I'm feeling good.