Do you need "portability" and "performance" at the SAME TIME?
If not, you can look into a tiny light machine w/ an eGPU, though that is $$$ it will do what you want.
Other option: Do you need a monitor or keyboard? If not, have you considered building your own in a portable case?
Otherwise I think you're SOL. Cooling is the main issue and if you really want good performance you may run into trouble going smaller.
For example, I have a lenovo x1 extreme w/ a 6-core i7 and 4GB Geforce 1650
It's a great machine--but it doesn't run as fast as you would think from the specs, because it is thin, light, and therefore limited by cooling. It simply cannot support continuous max-cpu wattage, much less continuous max-cpu and max-gpu.
No surprise: Think of how big a desktop cooler needs to be in order to dump 90w; look at the tiny ports in any thin/light laptop, and there's your answer.
Those same components that I have would be faster in the "normal" T-15 setup (which is cheaper, heavier, and larger), and faster still in the 17" (even thicker, larger, more cooling.)