Just thought I would pose this idea!!!
What about fabricate a discrete pulley system that takes off from where the super charger would normally attach, that then runs down a shaft that goes down the length of the motor (Between the motor and foot control rail) to the back then linking it to a supercharger with a suitable air filter in the airbox - even if you completely removed the airbox to gain the air flow...
I don't know what forces are involved in spinning up a supercharger and I would say machining may need to be extensive.
Could be a market for a stealth forced induction kit.