This place while it may seem unlikely, may be able to develop a bolt on supercharger. They do prototype tuning for manufacturers all the time. They did my supercharger on my '97 Vette.
The reason I am suggesting them (they do look like they only work on domestic V8s) is I saw a highly modified Ferrari 348 with twin-turbos on it being tuned by them. There was a place in Texas that built the system, but they couldn't tune it. Motec suggested they go to these guys. They've had people come as far as South Dakota if I remember correctly to have work done.
If you're serious about doing this, give them a call. They can only say no.