Here’s one source that seems more affordable, from a general search:
https://www.vevor.com/ultrasonic-cle...hoCprsQAvD_BwE
They list a 22 liter unit for $210 (460 W) and a 10 liter unit for $125.
From specifications, it seems decent but I have never used this outfit and cannot vouch for their quality.
I saw some do it yourself plans for building one, if you are so inclined.