I'm following this process of elimination...

1) Brett Stiles - Can't be him.  He would have been recognized at the Ellison Farms.  He doesn't fit the some young kid moniker used during the Ellison Farms episode.
2) Bob Kirkland - He is hunting RJ.  He is also dead now.
3) Bertram - The conversation with Reede Smith gave the impression that Reed is over Betram.  If he was Red John Reede would never speak to him like that.  I do feel he is part of Tiger Tiger though.

4) Thomas McAlister - I feel he is too old to meet the young kid reference made for the Ellison Farms - Couldn't find a reference to his age so perhaps I'm wrong.

Improbables:

5) Brett Partridge - He's dead.. Although I do wonder if he didn't fake his death to throw PJ off.  He is really my #2 choice.  I feel his voice fits RJ's voice much better than anyone elses.

That leaves Reede Smith and Ray Haffner.

I think Reede Smith is just a member of Tiger Tiger.

I'm going with Haffner as RJ.  He is a member of visualize.  He wouldn't answer the question about if he was at the Ellison Farms.  He was involved with the case where the PI got killed.. There was a reference made to he had other business to attend to that night.  He likes TL which is perhaps why he didn't kill her and just painted a face on her.  He has easy access to CBI, contacts, etc to keep up to date on the teams progress, etc.