Why limit yourself to just a TG ZED? If your carrier has staff agreements with SQ NH and UA get a combined ZED to cover all 4 carriers. Being able to use all 4 opens up many more flight options for you & gives yourself every chance of getting on a flight.
Even if you have to buy a seperate IDxx for some of those carriers, you can always cash them in (to help pay off the credit card bill on return to home !) if not used.
At least it's not Golden Week when you're trying to go!
Cheers