The worse problem to make a cable is to find stuff.
In many small towns it can be hard.
I suppose that if you have a computer you know some computer components,
and are able to find this stuff in computers stores of your town.
You can find DB9 in shops of electronic, computers or similars.
If you don't find 3 way shielded wire you can use two times a double wire.
Db9 plastic covering can also be replaced by epoxy.
I made my cable and the total enclosed was about US$ 5.00 (five dollars).
You can use also a mouse connection of 9 pins instead of DB9,
but it will increase costs to US$ 15.00.