Howdy, You can order an iGo from nHaler's website. I can't compare it's performance to the Joye Ego or the T-rex since I don't own either of them, but I've had no problems with mine. I got this tip from someone else when I was trying to decide:
go to Google and do the following search
site:e-cigarette-forum.com iGo
This should bring up some recent
threads on the iGo along with an iGo/GoGo/eGo/eTc. comparison.
There's a guy (I think his name is Bill) who has had wonderful things to say about them and hopefully might give you a better/more complete answer.
If it makes a difference to you, the iGo has 808
threading and I think the eGo is 510. not sure about the T-rex.
Good luck to ya.