I use these for my zipper locks most most and most people wouldn't know how to unlock these. I get these free from work is what I use at festivals to lock my bags.
Lucky Line 5” Twisty Lock Key Ring, Flexible Nylon Coated Steel Wire Loop, Corrosion-Resistant and Durable, Black, 5 Pack (8112005) https://www.amazon.com/dp/B013WB8WBM/ref=cm_sw_r_apan_i_KJ7C67PY55XFQG4YHGN6
I use something like this for my key ring. I've been using the same one for almost 10 years and I've never had it open unexpectedly. It's light, flexible, and easy to open.
2 of these. 1 for works hours and 1 for casual hours.
Work great, no bulk and lies flat. Flexible enough to minimize bulging. And the best thing, you don't have a janitor's carabiner jangling from your belt loop.
What I do is the following:
I have my entire keychain on one of these https://smile.amazon.com/gp/product/B013WB8WBM/
and its flexible enough that I don't have to remove the yubikey to plug it into anything. But if I ever need to remove it, its easy to do so.
I tried those Nite Ize S-Biner quick disconnects in the past for my bicycle key and the S-Biner broke