Is there any good iPhone stand with high-quality microphone for my desk?
There is no product that provides a stand and charger with a mic, but there are several external mics you can clip onto the iPhone. Some (lower quality) use the headphone jack, and some (higher quality) use the 30-pin docking port.

Here are two examples:

IK Multimedia iRig Mic Cast

This mic uses the headphone jack.



Tascam iM2W stereo mic

This mic uses the docking port, but has a pass-through USB connection that permits charging while the mic is in use.