Hobby Hoarder
I've designed three versions based on what I found online.
Hook
Has a very strong grip, it's impossible for your glasses to fall down with this. That's also it's downside; it's tricky to put them on and even harder to take them off. Because they're so thick, your ears might hurt after a while, as did mine.
Small hook
This one hopefully addresses the cons of the larger hook; it's smaller, so it shouldn't rub against your skin, yet it still retains the hook for a strong grip.
Ring
The ring is the best choice for daily wear. It won't help if you're doing some sort of sports, but apart from that, it performs excellent and it's the one I'd recommend to most people. It's what I'm using 99% of the time.
Blank versions
It's impossible to design a hole that will accommodate all the countless shapes and sizes of glasses out there. That's why I'm including a blank version of each design as well; simply import the blank into Tinkercad and cut out a hole that will fit your glasses.
Andrew Bahls
Tobias
Thomas Pointhuber
Tom Bailey