You mean the model kits of Going Merry?
I bought Thousand Sunny in one of the model kits store in BTS end of last year, can't remember the name of the store though. 
If my memory still serve me well, the location of the store is at the front row, which is facing the main hall.
Maybe you can try your luck there? 

try call af hobby,i think i saw it last week i went there..here the number 0102317202

You can try the figure shop in Lowyat Plaza, I saw quite a numbers there.

Not sure 1st of 2nd Floor dy, beside that shop is a bookshop

But beware alot bootleg there. Check it before buy