Use a forwarding company like Aramex Global Shopper (US$5 to join and R200 per package under half Kg) or buy from China using geekbuying or dx or banggood,...........
Correct indefinite article to use is "a" as the next word is a singular noun that does not start with a vowel or a silent "h". Although it is acceptable to use "an" preceding an acronym that doesn't starts with a vowel. So in fact both are correct.
Yip, tis what my English second language books also said. 'an' just sounds better because the beginning of FNB starts with the pronunciation of 'ef' (like 'an effect' which is correct vs 'a effect' which is not).