This is a tough one. The GL650 ignition switch is unique and no longer available. There are some online European parts sources that list a new GL650 switch, but the same part is also specified for GL500's. They are not the same.
It is possible to splice in a GL500 switch but it is not a simple plug-in operation. The GL500 switch is a little shorter, so it will be recessed slightly where the key inserts and will look a little odd. The GL500 contact base will not fit a GL650 switch.
If the problem is just the switch base cover, Honda part number 35102-431-007 can be trimmed to fit as shown below. A Dremel tool works well. The open areas can be sealed with Gorilla tape or similar.
In these first two photos, the new base cover is on the left.