if it were 1727 I could give you such a list ! (tho partial) - however coopers in 1927 were not that common and almost certainly worked for one of the three or so breweries on the Island rather than being self-employed - however the last trade directory is effectively 1894 though there were a couple of partial listings early 20th C so no real joy there.

It sounds as if he wasn't officially adopted thus if you know his birth name and date then apply for a birth cert from General Registry - that will give you mother's name. If you don't know his birth name then do you know the date of his birth ? - at one time I believe general registry would allow personal researchers to look through the index book if they knew the approximate date - it may be worthwhile contacting an on-Island researcher and seeing if you could get a list of those born at this period that look as if they could fit