I would agree that you will probably be able to get a shirt of better quality and price at your country of destination.
However, I work in a hot & humid area and fly low level in aircraft without air-conditioning and wear a cotton / polyester shirt. A small percentage of polyester (maybe less than 40%) has a number of advantages (ease of washing, better wear, less change of colour, etc).
100% cotton may not be the best answer unless you think that there is a significant danger of a flash fire!