I tried to find a good dropper via Aliexpress. I could only find a few models of the KS (Kind Shock) dropper, but the prices weren't low enough for me to purchase one.
I have 3 PNW Coastal Suspension droppers on 3 of my Aliexpress builds, and a 170mm travel PNW dropper on my most recent FRAMED 29er FS build.
I purchased all of these on sale at great prices over the past few years. (Usually between November and January.)