Do you means ESP-12 or ESP-12E ?
There are several pinout images but also pictures such as :
(beware that in the picture below, the GPIO4/GPIO5 were inverted in old batches)


Most of modules don't have themselves specs sheet, the above on is the chip itself, you can rely on it for whatever module you will be using.
About large quantity, I don't know. For small quantity, all ESPs (more than 10) have been purchase on eBay without any problems.