No worries, it did get pretty long and you probably just missed them 
@puzzlegal actually created a linked topic for you that lists the options we found: What options are there in wireless mice with a usb-c dongle?
Specifically, these all have small, true USB-C adapters (that can sit flush or nearly so against the laptop):
- Matias wireless USB-C in Black or White (small ambidextrous mouse)
- Matias wireless USB-C Pro in Black or White (larger right-handed ergo mouse)
- Lenovo Go in grey (small ambi mouse)
That other thread lists even more other USB-C mice, but the above three are the ones with the smallest dongles we found.