I don't think "Shada" will work without Romana and K9. Actually I take it back, River could replace Romana and since K9 is masterless right now, the Doctor could pick him up again.
What makes you believe K-9 is Master-less (Well, Mistress-Less). In the Classic Series, K-9 stayed on Gallifrey with Leela, K9 Mk II stayed at the CVE with Romana. The Audio Series Gallifrey Adventures doesn't make either one available to be picked up.
I think he's talking about Mark IV (the replacement for Mark III, which was destroyed in School Reunion).
Mark I - Stayed behind on Gallifrey with Leela
Mark II - Stayed in e-Space with the fake Romana
Mark III - Given to Sarah Jane as a gift by the Doctor (K9 and Company: A Girl's Best Friend), died in School Reunion
Mark IV - Also given to Sarah Jane by the Doctor
Ah, thanks, I had forgotten about Sarah Jane and her K9s (Mark I and II being so fresh in my head from Gallifrey Adventures and Classic Tom Baker, which I have just completed watching this weekend).
One Day I hope to be the Man my Cat thinks I am
Where are we going? And why are we in this Handbasket?