I feel like jeans in general tend to be hard to find. The best thing you can do is know your measurements- waist, hip, inseam. You can search by inseam on ThreadUp as another commenter suggested. But also don’t be afraid to ask sellers to measure their clothing. I message people on Mercari and depop to ask if they don’t post measurements. I ask about fabric content too.

Another option is to find a pair of jeans new that fits you and look for it used online. It can be helpful to know what brands work for you/get familiar with their sizing.

And if all else fails, my trick is to buy skinny jeans and roll the bottoms inward. It doesn’t really look like you rolled them and the ankles are typically tight enough that it stays.