You can add lead tape on your current racquet. Your local tennis or golf stores should carry lead tape. See Learning Center at
www.tenniswarehouse.com for customizing a racquet. I hide lead tape at 3 and 9 o' clock on the frame's outside under head tape; it is easier and provides more stability than placeing lead inside the frame.
Reminder: Lead is poisonous; do not digest; wash you hand after touching it.