Bit late to answer but in the UK I just tried a new scooter that was just released, and I am shocked. The brand is called shock wheelz - I ordered on amazon but they have a website I was just checking out. Pretty sure they deliver to USA.
Their GO model would probably be perfect for you it folds into 4 pieces and can fit in a backpack but its also just as durable and fast as most other models on the market. Its like $320,
I have had a Ninebot and Xiaomi and they both really don't compare! Especially when the Shock Wheelz model is so much more affordable.
Honestly, I have the PRO-MAX and I have never felt so safe compared to the other scooters I have used, going over bumps etc. seemed like air especially at speed I don't think I could go back now, keep recommending them to my friends because why reach so far into your pocket if there is a model available that does all the same as the Ninebot for example for half the price (I would actually argue that it is miles better...but let's not get into that)
What really p**d me off about my Xiaomi is that it didn't have a removable battery so I had to keep carrying the whole scooter inside and charging it next to my ironing board But now I don't have to at all the Shock Wheelz one comes out the middle stem and you just plug it in, can't believe I went to all that trouble before.