Someone didn't bother to do their home work. :P
Like ShadowWulf stated BOE makes a kit as he has linked to. Others (very few) have done the conversion by sourcing stock S parts. MonkeyWrench Racing sells a wonky kit but I wouldn't recommend it as well as the S supercharger itself.
The BOE kit makes some great power WAAAY above stock S power levels. I would opt for BOE's complete kit if I was going to have a go at it. At $12k plus another 20-30hrs of labor to install, it isn't cheap.
Moot point now but with the delta of the prices on the S1 S cars being not much more over a non S - compared to S/C'ing a non S - why did you go NA if you wanted to supercharge? Just asking, I have an NA myself and would love to SC! When I bought there was a big difference in price than what I found my 2011 NA for.
2005 Elise- Katana II Supercharged and other fun bits
2011 Evora - Daily Driver