[Dx4win] true RTTY with my laptop?

[George]

I want to run true FSK RTTY with MMTTY and DX4WIN on my laptop computer but
I can't get the MMTTY program to wiggle the FSK frequency with my USB to
RS232 FTDI-A36 cable. It will key my Icom 756 Pro2 but no FSK wiggle.
Is there a USB to RS232 (serial DB9) dongle out there that will do this,
model and where to buy? 
I'd like to do the true FSK vs. AFSK if possible with my laptop which of
course, does not have a serial DB9 port.
Thanks.

George  W2YJ