T&T: Opto isolated rs232 connector

[CAROL SIEGEL]

Years ago, when I first got the CAPN, it was recommended that it be 
connected to the computer via an opto isolated rs232 connector (DB9). 
At that time, if you bought the CAPN software, you could get the opto 
isolated cable/connector for a few additional bucks.
Looking for one of these today all I can find is some very costly models.
Anyone know if and where low cost models can be obtained?
The other side of the question is what is "todays" view of the need 
to use the opto isolated connector?

JULES SIEGEL K42 #188 CARINA