Hi Mike!

(I have not tested this solution, be careful
with your RS232 port and USB port).

Laptop Computer Serial Port Power Booster:
http://www.qsl.net/eb4eqa/serial_boo...al_booster.htm

Where to get +5V from USB:
http://www.siliconchip.com.au/cms/A_30612/article.html


Best regards,

Luciano