What seat has it at the moment?
If its the BMW Comfort seat they are a about an inch higher than standard. If you have the Comfort then a change to standard could help.
As seahorse has said, there was a low seat option and they do turn up from time to time. It does away with the side panels and the tool tray. Make sure all the bits are with it. They could be as rare as rocking horse poo.
Or you could go for a RAM shock from Realm Engineering. Good shock that can be ordered with a 1" reduction in length. You could drop the forks slightly to compensate.
One of the wackiest but cheapest options is to have an inch added to the heel and sole of your riding boots!
I know of at least one vertically challenged K100 rider who has done this.
Its actually more to do with the width of the seat where the tank meets the seat but hope some of these options might help.