Connecting hardware synthesizer to speakup without serial port.

[łukasz golonka]

Hi. I have apollo II synthetiser. I would like  to connect it to
speakup, but i have computers without physical serial port. Usb to
serial interfaces don't work with speakup of course. Is it possible to
connect speakup to apollo. I've heard about possibility to connect
external synthetiser to speakup using express card to com adapter, but
my computer doesn't  have  physical express card port, so i must again
use express card to usb converter.
Thank you for help.
Lukasz.