Anyone know where to get cheap US regional jets in the US?

Specifically looking for United Express 1:400 aircraft. Can't find any for a price under 150$, and for some reason no one is releasing any. For Delta Connection aircraft, I'm relatively fine, as they go cheaply. My big problem is just United Express, as I need a lot of them, yet I can fine none online. If anyone knows anywhere to get them cheaper, or are selling any, let me know.