The port sizes are as follows.
~8mm for both the ports on the throttle body.
~10mm for the smaller port on the heat exchanger.
~13mm for the larger port on the heat exchanger.
Were as you can stretch an 8mm I.D. hose up to 10mm. It's not possible with such a big jump for the larger 13mm (1/2") port.
Option A. You could split the difference and maybe use a 10mm hose and hope it clamps well enough on the smaller port.
Or option B. Use a reducing fitting or hose.
I managed to find a really nice, 90 degree 12mm to 8mm silicone reducer this week that should do the job. I also picked up another that's 8mm at both ends to help with the angles.