I've found an old picture of a cable layout:

you need:
1 Sub-D9 Female connector
1 Jack Stereo Ø2,5mm

if you number the D9 as follows:

5 4 3 2 1
9 8 7 6

And if you call the layout of the Jack as follows:

/ \ = A
| = B
| = C

You need to connect:
2 with A
3 with B
5 with C

Gert-Jan