I wasn't able to find much information on the T1R midpipe... nothing relatively recent anyways. Looks like it was a thing back when the GTR was just released. Two 70mm pipes (smaller than usual?) coming in to one 90mm exit. I'm not really sure if that middle section is supposed to be a resonator or not. I think that's the reason your having such trouble finding one, It doesn't appear to be a very popular choice at all.
I believe someone from Speed By Design has already contacted you in the past about trying our 90mm Non-resonated midpipe, but I'd be happy to re-visit the subject with you if you'd like to work out a deal on ours.
Woohoo! It's our lucky day! I just purchased a T1R Exhaust off of a friend and have a brand spanking new T1R mid pipe coming with it that I won't need, Since I just ordered a new AMS Alpha resonated Mid pipe! I'll absolutely set you up with it Z3GTR! It should arrive at my house Tuesday this week!