I believe you can also get a 2.5mm from Radio Shack. Just ask the guy.
How I made my parallel link:
I followed the instructions for the parallel port schematics, but
instead I used the wire and jack of a broken stereo headphone that I found in
my garage (I must have like 10s-20s of them lying around garage). I then
bought a head-phone jack to 2.5mm jack converter for sound and for my
parallel link.