I have a black compact K3 manual for sale.
It has 58mm flat burrs, making it similar to the DF 54 but slightly better. This was made with single dosing in mind, so retention is not horrific.
It's in functionally good condition and was recently cleaned. The burrs were also aligned, so it grinds well for espresso. It has stepless micrometric grind adjustment. It'll be difficult to find something as nice and reliable as this at this price point-the Chinese DF grinders have all sorts of jamming issues that this just doesn't.
More pictures upon request.