I have a several years old (bought it in 2008, IIRC, but it just worked on
my craptastic bench board where I was reading temperatures for a test) 4
pin header to DB9 w/ included DB9 to USB adapter which came with my
nerdkit. It's got a part # of P97132 on it, and it uses a TI CD74HCT14E
Think it'll do what you want?
And yes, I'd buy one from Brad, too, but if you seriously just need to
borrow one for testing and this'll do, you're welcome to use it. I'll be by
the space fairly early tonight, I think. I'm only 2 blocks away.