This is probably something of a long shot but I play the Fifth Doctor over at islandkeepers and would give my left arm for a Vislor Turlough. My Doctor doesn't know Turlough yet but it would be nice to get a companion from Five's era into the mix. If you're more interested in someone he won't be momentarily confused with I'd also love a Tegan or Nyssa.
If you aren't interested in that I would love a psl against any of the newer companions