Например: (http://ru.aliexpress.com/item/Free-Shipping-USB-to-RS485-485-Converter-Adapter-Support-Win7-XP-Vista-Linux-Mac-OS-WinCE5/1896086704.html , http://www.dx.com/ru/p/usb-to-rs485-module-black-221402?tc=RUB&gclid=COavlbDOgb8CFeHbcgodIjUAOg#.U6CSrv53TFU )