The Siri is small, rechargeable, made of silicone and plastic, multiple settings and speeds, and fairly quiet. But it's not even splashproof and will definitely be an obvious vibrator if found.

The Little Chroma is even smaller, even quieter (almost 0 noise!), waterproof, but takes battiers, has only one setting, and can not go through a metal dectector. But if you put it in a carry on without batteries, it looks like a weird pen or tiny flashlight.

The rest of my vibrators range from moderate noise level to high so those are the ones I own that I'd recommend personally. But I know there are so many other new super quiet ones nowadays.

The Little Chroma would be great. You can even take the motor out to make sure nothing suspicious happens. No need for chargers to tip people off to its presence, just bring extra batteries. There's a little noise as you're getting the cap screwed on tight, but once it's on there, it's almost silent. Also, if you do leave it where someone might see it (or you have relatives who snoop), it's a lot more discrete a toy than, let's say, some big phallic thing. If you don't need a dildo built in, it's pretty much the ideal discrete travel vibe. You can also take it in the shower for bonus privacy.

Small and quiet is the trick. I usually just stick with my girlfriend and her magic finger during these times. She can do it better than any toy and I like to say I do it just as well as hers if not better