That looks homemade to me. It's a Roots blower from the looks of it, Paxtons look like the compressor end of a turbocharger with a belt/gear drive instead of an exhaust turbine. There are/were quite a few hyper tuned 660cc Japanese cars using Roots superchargers, places that sell performance parts for Japanese cars might be able to help you. The Aisin AMR300 (Subaru EN07) and AMR500 (Nissan MA09) would work pretty well and are quite small. Japanese car laws are pretty strange and "old" cars (6+ years) get more and more expensive to license. Japanese people generally take insanely good care of their cars. These facts mean that there is a good supply of used stuff for domestic-only cars over 6 years old (parts for exported models have a ready market worldwide but Japan only stuff - like the hyper 550 and 660 engines - is harder to sell anywhere else). Japanese wrecking yards are an amazing sight, piles of new looking Toyotas and Nissans.
In general a Roots blower gives a lot of boost at low RPM, it is a positive displacement pump and the blower ratio sets the max boost at low speed - ie a 750cc per turn blower with a 2:1 drive would give 1 bar boost on a 750cc engine but at high RPM the boost drops as intake vacuum and flow effects bite into the efficiency. A Paxton blower, basically a centrifugal fan, has boost that increases with higher revs. It feels basically like a turbo with no turbo lag.
You need a cam grind with little or no overlap to make the most of any pressurized intake system.
