Your best bet would be to purchase a new interface. Decent USB interfaces can be had for a little as $30.
Once you have a good interface, pick up an inexpensive small format mixer like a Yamaha, Soundcraft, etc. and then you can buy any microphone you want..
I set up small systems like this for clients who have pod casts, who are psychologists and want to record their sessions, therapists, etc.
One of the cheapest, but still decent systems is to buy a fifty dollar Behringer mixer and an MXL 990 mic. Put the mic on a desk stand, connect your music to the mixer, the mixer to the computer and you are ready to record.
Total cost with a USB interface is around $150.
When you decide to upgrade, it is a simple matter to just buy a better mic, or a better mixer.
WARNING! INCORRECT USING THIS FEATURES MAY CAUSE YOUR SYSTEM BROKEN!