These knot come in 20mm, some as small as 18mm:
Boti Brush 2022 New Tuxedo Ceiling Thick Hair 5th Handmade Synthetic Hair Knot
Boti Brush-Pro Synthetic Hair Knot 3 Color Imitate Badger Hair Bulb Type Class B
Boti Brush-Handmade The Newest 3 Color Synthetic Hair Knot Fan Shape
I will search for them.