Very good question. The best answer I can give is that there just are not that many examples of "Charlie Chan at Treasure Island" posters available. There is a gentlemen from New York City (the foremost Chan poster collector in the world) who owns one and has told me of the rarety of "same." It would stand to reason to me that since this is the case, that those who would seek to make fine reproductions would not be able to find an original from which to make a copy.
The above is, of course, assuming that you seek a facsimile of a "Treasure island" poster. I have only seen ONE original poster up for purchase/auction, and, you can be sure that the price wuld be a bit steep.
At any rate, thank you, again, and good luck in your search.
