PNW Coast Suspension Dropper Post. 100mm of drop, it also provides a little bit of suspension. I liked this post a lot but it doesn't work for my current bike. Hasn't been used much, really good shape. Comes with a generic thumb lever.
Or, for another $30 I have a Shimano XTR SL-MT800 Dropper Seatpost Lever.
Info here: https://pnwcomponents.com/products/coast-suspension-dropper-post-external?variant=40010488021069