Where can I purchase a bigger lens for a Konica Minolta Dimage 7 Camera?

One that is cheap but good and what kind should I get?

The Dimage 7 has a fixed (not removable) lens with a 49mm filter thread size. The only thing you might be able to do is to attach a telephoto adapter to the front of your lens - for example:
http://cgi.ebay.com/Tokina-3X-HIDEF-TELE...
It's a cheap solution - but don't expect great results.

try ebay