Banks generally deal in United States currency, and while the U.S. Mint produces gold coins for collectors and investors, they are not legal tender and not handled by banks. Most people buy gold coins from private gold dealers or from the U.S. Mint.
Private companies, and some countries, produce decorative and commemorative disks of gold bullion. While commonly called coins, they do not have a set monetary value and so are not technically currency. Their value fluctuates with the spot value of gold. Prior to 1933, several actual U.S. coins were minted in gold, and many are available from coin dealers.