https://www.amazon.com/UGY-Acoustic-Electric-Guitars-Ukulele/dp/B01N1HJKKX/ref=sr_1_3?s=musical-instruments&ie=UTF8&qid=1535347300&sr=1-3&keywords=ukulele+capo This appears to just be a guitar capo.

I feel like you're overthinking it, capos are just clamps. You can make a capo with a pen and a rubber band. Some ukuleles have smaller/larger necks than others, but any spring loaded capo should work perfectly fine. With the screw on capos, I can see an issue with sizing.