Oh - you find it sort of lying around the place when offices you work in are being refurbished...BAS, OT to the OP but how do you find brand-rex cable.
And no - I didn't just blag it when no-one was looking - when the installers got to the end of a 1000' reel and what was left wasn't long enough for runs in open-plan offices, they chucked it out - wasn't worth their time trying to sort and keep odd lengths to use if they needed a short run.