If you do manage to find 1, don't stress out about it, you can store it in a wagon and store it at another town and wait until your guild gets a guild house. It can still be used for guild crafting WAY past its expiration timer.
Yes, it's correct. You make the Dried Pearl Oyster Flesh by drying the Giant Pearl Oyster. Initially you've used wrong name "Dried Pearl Oyster Flesh". Looks like there is a some misunderstanding or translation problems here