Despite what your dealer has told you, Key blanks are available. If your bike is a People GT300i, the PN's are:
35111-LDC1-305-M1 (Right Hand Blank)
35111-LDC1-305-M1 (Left Hand Blank)
35111-LDC1-307-M1 (Shutter Key Fob)
You will need the know what bank you need, Right or Left side cut. Look at your old one, dealer should be able to identify.
CJS